Just 17, Song earned the first-round lead with a bogey-free, 6-under 66 at the Mission Hills Country Club. She was a stroke ahead of 22-year-old Lorena Ochoa of Mexico, Rosie Jones and Scotland's Catriona Matthew.
"I hit the ball really well for a majority of the day," said Song, who first played in this event when she was 12. "It was fun."
Song is a rookie on the LPGA Tour. Wie is still an amateur, but the 14-year-old from Hawaii posted a 3-under 69.
"It is amazing they can play so well at a young age," said the 34-year-old Matthew, who was Scottish Girls champion before either Song or Wie was born.
Karrie Webb and Dottie Pepper were two shots off the lead while Sorenstam shot a 71.