Kvitova, the No. 9 seed, beat world No. 6-ranked Sara Errani 6-4, 6-7 (3-7), 6-3 for her second win over a Top 10 player in five days. She beat ninth-ranked Angelique Kerber in Saturday's final of the Japan Open.
She battled Errani for 2 1/2 hours and recorded 11 breaks over 16 receiving games which offset her own eight dropped service games. Kvitova improved to 6-0 lifetime against Errani, with all three matches this year going three sets.
Li, seeded fourth and a huge fan favorite in China, defeated 13th-seeded Sabine Lisicki by converting 4-of-5 break opportunities. She had a pair of breaks in each set.
No. 3-seeded Agnieszka Radwanska was among second-round winners Wednesday as she defeated Madison Keys 6-3, 6-2 by winning two-thirds of the points on serve and half when Keys served.
Also Wednesday, eighth-seeded Jelena Jankovic fought off 10-of-12 break points for a 6-3, 5-7, 6-3 win over Galina Voskoboeva but Polona Hercog eliminated 14th-seeded Ana Ivanovic 6-4, 6-4. Andrea Petkovic topped Svetlana Kuznetsova 4-6, 6-4, 6-1 in a battle of unseeded players.
Swim Week Miami Beach 2014 [PHOTOS]