SANYA, 27 Oct, 2014 (AFP) - The 33-year-old finished on 200 with a five-under 67 in the third and final round, leaving her three strokes ahead of Germany's Caroline Masson overall.
"I can’t actually believe it," Pace said.
"I’m still so in the moment of one shot at a time that I think it’s going to hit me. It’s like, literally 'Now I can relax'. It’s amazing. Obviously one of my life goals."
Pace fired five birdies in her bogey-free round, while Masson ripped through four birdies in her final six holes.
"I’m happy with that finish and that was all I could do," said Masson.
Americans Michelle Wie and Jessica Korda finished third on 205.
The pair both made two bogeys in the final round as they lost touch with the lead.
The Jian Lake club was hit by heavy rain during the tournament, with organisers forced to reduce the $2 million event from four rounds to three and extend it to Monday.
Pace claimed her ninth Ladies European Tour victory at the South African Women's Open last week.
She is the second South African-born player to win on the LPGA Tour after 15-time champion Sally Little.
LPGA Blue Bay Championship scores
200 - Lee-Anne Pace (RSA) 67-66-67
203 - Caroline Masson (GER) 67-69-67
205 - Michelle Wie (USA) 67-68-70, Jessica Korda (USA) 66-67-72
206 - Danielle Kang (USA) 68-68-70, Chella Choi (KOR) 68-66-72
207 - Lydia Ko (NZL) 69-70-68, Feng Shanshan (CHN) 67-68-72
208 - Jenny Shin (KOR) 71-70-67, Brittany Lang (USA) 67-68-73
209 - Thidapa Suwannapura (THA) 70-72-67, Cristie Kerr (USA) 68-73-68, Dewi Claire Schreefel (NED) 68, 72, 69, Belen Mozo (ESP) 72-67-70, Mariajo Uribe (COL) 69-70-70, Austin Ernst (USA) 71-66-72
210 - Ilhee Lee (KOR) 73-68-69, Sandra Gal (GER) 70-71-69, Lu Wanyao (CHN) 69-68-73