Williams needed just over one hour and four minutes and never looked in trouble with another display of powerful tennis on a court where she has looked very much at home in recent years, Xinhua reported.
Peng Shuai cannot be accused of giving up, but was just unable to compete with Williams' powerful hitting.
Number 4 seed Simona Helep defeated Spain's Lara Arruabarrena 6-4, 6-4 and number 14 seed Carla Suarez Navarro also progressed into the last 16 with a 6-2, 6-4 straight set win over America's Alison Riske.
Italy's Roberta Vinci produced a minor shock as she beat number 13 seed Carolina Wozniaki 6-3, 6-3 in a comfortable straight sets win.
Wednesday was all about Rafael Nadal in the men's competition as the world number one handed a crushing defeat to Argentina's Juan Monaco.
Fans have had to wait a long time to see Nadal and he was at his best after recent defeats in Monte Carlo and Barcelona with a win that needed just one hour and nine minutes.
Number 6 seed Tomas Berdych showed he was in fine form as he blasted past South African, Kevin Anderson, 6-1, 6-4 in one hour and 10 minutes.
Number 9 seed John Isner also progressed thanks to 6-7 (11-9), 7-6 (7-5), 7-5 victory over Marinko Matosevic in a game lasting 2 hours and 38 minutes and the number 12 seed Grigor Dimitrov is also into the third round on the back of a tense 4-6, 6-3, 7-6 (9- 7) win against Mariol Copil.
Lucasz Kubot and Alexandr Dolgopolov have also progressed into the third round.