The world number one took his record in Beijing to 26-0 in five visits as he beat China's number one 6-2 6-1.
Djokovic, 28, goes on to face Australian John Millman or American John Isner in the last eight.
Croatia's Ivo Karlovic became the all-time leader in aces as he hit 26 to reach 10,247, passing compatriot Goran Ivanisevic's record of 10,237.
"It's a great feeling," said 36-year-old Karlovic. "For the past year I knew it was possible and I was hoping that it would be this year. It's great that it happened here.
"I'm not done yet. There are many years in front of me and hopefully that number will go up and up."
