Wentworth, England, May 27, 2012 (AFP) - A year after becoming number one for the first time at the same event Donald was back at the head of the list for the fourth time in his career.
The Englishman carded a four-round total of 273, 15-under par and won by four shots from Scotland's Paul Lawrie and Justin Rose from England.
Rose, who missed a six foot putt at the last which would have given him second place outright, had put the pressure on during the front nine before Donald eased away to win and displace Rory McIlory as world number one.
The 34-year-old said: "There is something special about going 12 months and still being number one. We have swapped it a couple of times but to go a 12 month span is something I am very proud of and is a vindication that what I am doing is right and shows that my game is improving."
This was a much more comfortable win for Donald than last year's when he had to win a play-off against Lee Westwood to take the crown.
Donald said: "I enjoyed the walk up the 18th more this time with a four-shot lead. It is very special to come back here - this is the biggest event we play on the European Tour.
"I played nicely for the whole week but today was the most difficult day in terms of pressure. I had a two-shot lead but I was trying to defend and I had never successfully defended a title before.
"I felt some tension out there - it is not easy going out with a lead and trying to close out a tournament. Justin is a solid player and I knew he was not going to give it away - I had to go and earn it."
Scotland's Lawrie had a best of the day 66, six-under par, had only one bogey on his card and finished with a flourish by birdying the last two holes, both par-5s to add to the three other birdies and an eagle he had already collected.
And the Scot claimed his high finish proved he made the right choice in playing here and skipping the US Open next month.
He said: "I made my decision a long time ago that it was better for my schedule not to go across to America at that time. It means I can have two weeks off and then go straight through to the British Open. I knew some people wouldn't like it but it is the best for me.
"The big priority for me is to get back into the Ryder Cup team and I feel the US Open is not a venue that's ever suited my game."
Ireland's Peter Lawrie, who had shared the lead after the first round, had two birdies in the first seven holes but his hopes went up in smoke with a triple bogey seven at the eighth and he finished on 280, level par and in fourth spot with South African Branden Grace a further shot back in fifth.
Donald became only the third player to win back-to-back PGA titles following in the footsteps of Sir Nick Faldo (1980-1981) and Colin Montgomerie, who won three times from 1998 and this was the fourth English win in a row here after Paul Casey, Simon Khan and Donald's first victory last year.
Rose got level with Donald with back-to-back birdies at the third and fourth whilst Donald dropped a shot at the fourth. However Donald responded by holing putts of 15 and 18 feet at the sixth and seventh to go clear again.
Donald played serene golf for the rest of the back nine making up shots at the 10th, 12th and 16th whilst Rose bogeyed the 16th after hitting his second shot into a greenside bunker and Donald shut the door.
Final scores from the PGA Championship here at Wentworth on Sunday (par 72):
273 - Luke Donald (ENG) 68-68-69-68
277 - Paul Lawrie (SCO) 69-71-71-66, Justin Rose (ENG) 67-71-69-70
280 - Peter Lawrie (IRE) 66-71-72-71
281 - Branden Grace (RSA) 69-69-73-70
282 - Richard Sterne (RSA) 71-68-72-71
283 - Marcel Siem (GER) 71-67-76-69, Francesco Molinari (ITA) 68-70-74-71, Ernie Els (RSA) 68-73-70-72
284 - David Drysdale (SCO) 66-70-78-70, Alvaro Quiros (ESP) 67-70-77-70, David Higgins (IRE) 70-70-74-70, James Morrison (ENG) 68-64-81-71, Ian Poulter (ENG) 71-73-69-71
285 - Martin Kaymer (GER) 71-69-76-69, SSP Chowrasia (IND) 69-76-71-69, Rafa Cabrera-Bello (ESP) 68-70-74-73
286 - Charl Schwartzel (RSA) 69-71-79-67, Fredrik Andersson Hed (SWE) 70-68-77-71, Peter Hedblom (SWE) 68-70-74-74
287 - George Coetzee (RSA) 68-77-76-66, Paul Streeter (ENG) 71-74-74-68, Robert Rock (ENG) 68-76-74-69, Victor Dubuisson (FRA) 70-71-76-70, Alexander Noren (SWE) 70-74-73-70, Julien Quesne (FRA) 74-71-72-70
288 - Jose Maria Olazabal (ESP) 70-72-76-70, Garth Mulroy (RSA) 71-70-76-71, Marc Warren (SCO) 68-76-72-72, Simon Khan (ENG) 71-74-70-73, Federico Colombo (ITA) 69-74-71-74, Jeev Milkha Singh (IND) 70-74-70-74
289 - Jbe Kruger (RSA) 72-73-74-70, Niclas Fasth (SWE) 67-73-78-71, Richard Finch (ENG) 76-67-74-72, Paul McGinley (IRE) 73-71-73-72, Ricardo Gonzalez (ARG) 71-67-77-74, Lee Westwood (ENG) 70-75-70-74
290 - Andrew Dodt (AUS) 69-73-76-72, Damien McGrane (IRE) 71-72-75-72, Miguel Angel Jimenez (ESP) 71-70-76-73, Gareth Maybin (NIR) 70-70-76-74
291 - Thomas Bjorn (DEN) 74-70-78-69, Matteo Manassero (ITA) 74-69-77-71, Danny Willett (ENG) 69-71-79-72, Kenneth Ferrie (ENG) 68-74-77-72, Scott Jamieson (SCO) 68-75-75-73, Richard S Johnson (SWE) 67-75-75-74
292 - Chris Wood (ENG) 73-71-80-68, Alex Cejka (GER) 75-70-76-71, Tommy Fleetwood (ENG) 72-73-72-75, Edoardo Molinari (ITA) 69-70-76-77
293 - Bern Wiesberger (AUT) 68-73-83-69, Jamie Donaldson (WAL) 67-73-77-76, Pablo Martin (ESP) 69-70-76-78
294 - Thongchai Jaidee (THA) 71-72-79-72, Jose Manuel Lara (ESP) 72-71-78-73, Christian Nilsson (SWE) 74-70-77-73, Sam Little (ENG) 72-73-76-73
296 - Gregory Havret (FRA) 75-67-83-71, Steve Webster (ENG) 69-74-81-72, Robert-Jan Derksen (NED) 71-71-81-73, Mikko Ilonen (FIN) 74-70-79-73, Bradley Dredge (WAL) 71-72-78-75
297 - Oscar Floren (SWE) 74-71-80-72, Richard Green (AUS) 72-73-79-73, Pablo Larrazabal (ESP) 70-75-77-75
298 - Ben Curtis (USA) 70-75-81-72, Shane Lowry (IRE) 71-74-79-74
301 - James Kingston (RSA) 71-74-85-71, Brett Rumford (AUS) 70-74-79-78
302 - Colin Montgomerie (SCO) 69-74-78-81