The Spanish world No 1, enjoying a late-career flourish, dispatched Russia's promising Karen Khachanov 6-3 6-3 on the outside hard court in Beijing.
Nadal, the top seed and coming off the back of a third US Open title, faces big-serving American John Isner in the last eight.
The 31-year-old Nadal broke Khachanov, ranked 42 in the world, in the fourth game and was never in serious trouble after that.
Khachanov, at age 21 a rising talent, simply had no reply to Nadal's explosive forehand and made too many routine errors.