MELBOURNE, November 22, 2013 (AFP) - The 42-year-old, who made his last Royal Melbourne appearance eight years ago, moved to eight-under par in bright but testing conditions.
The reigning Omega European Masters champion sandwiched five birdies in between first and last hole bogeys.
"There were a couple of instances today that really tested me as I three-putted the first but then after that I kind of patiently worked my way into the round," Bjorn said.
"I didn't play quite as good today on the front nine as I did on day one, but on the back nine today, I played awesome despite three putting 14 and then got a bit unfortunate on the last," he said.
Golf returns to the Olympic Games in 2016 for the first time since 1904.
For this reason, the International Federation of PGA Tours has changed to a World Cup format to mirror the intended format of competition in Rio de Janeiro.
Bjorn is currently ranked 44th in the world and 14 places ahead of the next best Dane in 23-year-old Thorbjorn Olesen and his playing partner this week.
At this stage it will ensure Bjorn will qualify for all four Majors and all four WGC events next season.
When golf does return to the Olympics Bjorn will be 45 years old, however he has shown he has lost none of his competitive edge, winning four of his 17 career European Tour victories since turning 40.
"It's always been in my mind to compete in at least one Olympic Games," Bjorn said.
"Since turning 40 I have been playing some of the best golf of my career but then I also have to stay healthy and stay focussed."
Bjorn singled out Paul Elvstrom, one of Denmark's greatest-ever summer Olympians, who competed in eight Olympic Games from 1948 to 1988, winning four gold medals.
"What Paul Elvstrom achieved in sailing for Denmark was remarkable so to just tee up in Rio de Janeiro representing Denmark in an Olympic Games would be incredible, but... (there are) many more years before I can begin to think like that" said Bjorn.
American Kevin Streelman birdied his opening four holes but then dropped three shots at the eight and ninth holes in a round of 68 to be in second place on seven under par.
Australia's Jason Day (70) and Portugal's Ricardo Santos (69) are tied in third place on four under par.
World No. 2 and reigning Masters champion, Adam Scott posted a 68 to be lying in a share of 21st place at one over par.
In the team event it is the defending American pair of Streelman and Matt Kuchar, who shot a second round 68, who lead by three shots with a 10-under par tally.
Australasian PGA Tournaments Director, Andrew Langford-Jones has defended criticism from a number of players, including Australia's Jason Day, that the hot and windy conditions are making parts of the Royal Melbourne course 'unfair'.
"The greens staff have had challenges preparing the course for back-to-back tournaments and while the greens have compacted a bit, the Federation of Golf Tour's view is that the set-up of Royal Melbourne is where we were hoping it would be," Langford-Jones said.
Leading 2nd round completed scores - ISPS Handa World Cup of Golf, Royal Melbourne G C, Melbourne, Australia. Par 71; 6441 metres, 7046 yards.
INDIVIDUAL
134 - Thomas Bjorn, Denmark 66-68
135 - Kevin Streelman USA 66-69
138 - Ricardo Santos, Portugal 69-69
138 - Jason Day, Australia 68-70
139 - Martin Laird, Scotland 67-72
139 - Stuart Manley, Wales 67-72
139 - Hideto Tanihara, Japan 72-67
139 - Matt Kuchar, USA 71-68
141 - Tony Lascuna, Philippines 70-71
141 - Oscar Fraustro, Mexico 74-67
141 - Gregory Bourdy, France 72-69
141 - K J Choi, South Korea 67-74
141 - Kiradech Aphibarnrat, Thailand 71-70
141 - David Hearn, Canada 70-71
142 - Anirban Lahiri, India 72-70
142 - Danny Willett, England 68-73
142 - Vijay Singh, India 73-69
142 - Ryo Ishikawa, Japan 71-71
142 - Francesco Molinari, Italy 75-67
142 - Miguel Angel Jimenez, Spain 75-69
Notables
143 - Adam Scott, Australia 75-68
143 - Graeme McDowell, Northern Ireland 72-71
TEAM SCORES
USA (Streelman/Kuchar) 274
Denmark (Bjorn/Olesen) 277
Japan (Ishikawa/Tanihara) 281
Australia (Day/Scott) 281
Portugal (Santos/Lima) 282
Scotland (Laird/Gallacher) 284
Thailand (Aphibarnrat/Marksaeng) 285
France (Bourdy/Dubuisson) 285
Canada (Hearn/Fritsch) 285