Dustin Johnson equalled the course record with a 63 to move five shots clear after round two of the World Golf Championships event in Shanghai.
The American made 10 birdies to surge clear of the field in China.
After shooting seven under par on the opening day, the progress of Northern Ireland's Rory McIlroy's stalled with an even-par round of 72.
McIlroy has a share of second place with Americans Bubba Watson and Boo Weekley heading into the weekend.
Ernie Els, Sergio Garcia, English duo Tommy Fleetwood and Ian Poulter and Northern Ireland's Graeme McDowell are in the group tied for fifth at six under.
Johnson picked up birdies at six of the opening seven holes and, after dropping a shot at the 10th, he secured a fourth birdie of the back nine on the 18th to card nine under par for his second round.
After his fine effort on Thursday, McIlroy, who started the second day with a two-shot lead, began with three birdies on the front nine.
But he struggled on the back nine, dropping two shots before finding the water as he tried to reach the par-five 18th in two - resulting in another bogey.