Li, who won the 2011 French Open and was the losing finalist here to Kim Clijsters the same year, broke Sharapova's serve in the fifth and seventh games of the second set on Thursday.
Sharapova had dropped only nine games in five matches en route to the semifinals, a tournament record.
The sixth-seeded Li, who has been working since August with Justine Henin's former coach, Carlos Rodriquez, will play either defending champion Victoria Azarenka or 19-year-old American Sloane Stephens in Saturday night's final.
More Sports Headlines
Snohomish mixed martial artist returns to her first love Mariners beat Twins 4-3 in 11 innings Charles scores 29 points, Liberty beat Storm 78-62 Park wins Women's British Open, captures 4th different major Perry wins 2nd straight Champions Tour's 3M Championship Merritt shoots 67 to win Quicken Loans National by 3 shots Triple Crown winner American Pharoah wins $1.75 million Haskell Invitational Bills' Ryan names Incognito starting left guard
Our new comment system is not supported in IE 7. Please upgrade your browser here.