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.
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