Louis Oosthuizen hit a nine-under-par 63 to lead by five shots after round two of the WGC-HSBC Champions tournament in China.
The South African shared top spot with Adam Scott after the opening round, but he hit eight birdies and an eagle on his way to equalling the event record.
Scott hit a round of 68 to share second place with Open champion Ernie Els, who also recorded a round of 63.
Ireland's Shane Lowry followed up his first-round score of 66 with a solid 68 to lie in fourth place with Jason Dufner.
World number three Luke Donald led the English challenge with a second successive round of 68 to leave himself in ninth place at the halfway stage.
