The 19-year-old Park, who has dual Brazilian and American citizenship, had a total of 14-under 202. Taiwan-born Candie Kung, who also has U.S. citizenship, was one shot back after a 67.
I was playing mediocre throughout the whole round, Park said. I didnt see anyone else go extremely low so I tried to stay positive and it came around.
Julie Inkster of the United States, the 2003 Evian champion, was third at 11 under after a 69, her third straight sub-70 round. Swedens Helen Alfredsson, who trailed Park by one stroke after a course-record 63 Friday, was four shots back in fourth following a 71.
Park is looking for her first LPGA victory, and has never led after 54 holes.
I have no strategy so far, she said. Just hit fairways and greens and be patient out there.
Top-ranked Lorena Ochoa had a 70 to be one of four players tied for seventh place, six shots behind Park.
Im a little frustrated, said the 26-year-old Mexican, who led after a first-round 65. I was really close to shooting a low round, but I couldnt make any putts. I can do it. I am going to be positive, hopefully I can start good and go from there.
Park made two birdies on the front before missing a short par putt at 13, her only bogey of the tournament.
Like Park, Kung also grew up in Southern California and now lives in Allen, Texas.
This weeks been pretty good for me, said Kung, whose three LPGA wins all came in 2003. This will probably be the first time (since 2003) being in the last group. Its going to be fun.
The 43-year-old Alfredsson battled through a round of five birdies and four bogies.
It was an adventure, she said. I was fighting and never got it going like (Friday). Sometimes it is such a letdown after you have a round like that. I hit some shots I didnt recognize. But I kept in there and Im not totally displeased.
Annika Sorenstam, who is retiring at the end of the season, is unlikely to earn a third victory at Evian after winning here in 2000 and 02. A 73 left the 37-year-old Swede 11 strokes off the lead.