The top-seeded American, who has won more than $9 million in prize money in 2013, broke Wozniacki twice to breeze through the first set in 26 minutes.
Williams continued her dominance in the second set, breaking Wozniacki in the first and third games to go up 4-0. The Dane fought back, closing the gap to 4-3, but it was not enough to stop Williams from winning the set 6-4.
"I felt I played really well tonight, especially in the first set," Williams told reporters. "I played well in the second set too, but I think Caroline just played so much better and she lifted her game so much.
"But I think overall it was the best performance I've had this week, which I'm excited about."
Third-seeded Agnieszka Radwanska will be up next for Williams, who took her number of wins in 2013 to 71.
Ninth-seeded Czech Petra Kvitova broke the hearts of the crowd when she rallied to beat home favourite Li Na, seeded fourth, 4-6 6-2 6-4.
The former Wimbledon champion set up a semi-final date with Serbian Jelena Jankovic, who won a two-hour, 36-minute match against Czech Lucie Safarova 6-7(3) 6-4 6-4.
Radwanska, who has never beaten Williams in their previous six meetings, defeated seventh-seeded German Angelique Kerber 7-6(7) 6-4 to complete the semi-final line-up.
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