Ochoa, who took over from Sorenstam as the world's No. 1 female golfer in April 2007, fired a 1-under 71 Friday on a difficult day to score at the Mission Hills course. That left her at 5-under 139 for 36 holes of the Kraft Nabisco Championship, the same score posted by Heather Young.
Sorenstam moved into a share of fifth place at 141 with Hee-Won Han. First-round leader Karen Stupples shot a 75 and was tied for seventh at 142.
Ochoa, who bogeyed her final hole in the opening round, bogeyed twice in the final six holes Friday.
She is seeking her second straight LPGA major championship. She won the Women's British Open last year.