The Spaniard, who saved two match points in a testing opening match against Lucas Pouille, was imperious under pressure as he fended off all six break points he faced.
He will face John Isner in the last eight after the American sixth seed thrashed Leonardo Mayer 6-0 6-3.
China Open men's results
Federer 'really inspired' by Nadal, hopes to 'hit ground running' on return
1-Rafa Nadal (Spain) beat Karen Khachanov (Russia) 6-3 6-3
6-John Isner (US) beat Leonardo Mayer (Argentina) 6-0 6-3
French Open: Who has the best draw? Who are the dark horses?
Raducanu, Swiatek to face qualifiers, Osaka gets tough opening clash
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