The US Open champion will face Karolina Muchova of the Czech Republic or Spain's Cristina Bucsa in the last eight in Beijing.
World number two Sabalenka has won more matches on tour this season than anyone else and extended her red-hot streak with a fairly routine victory over the 24th-ranked American.
On a sunny Beijing day, Sabalenka and Keys exchanged breaks in the first set for 3-3 before the hard-hitting Belarusian pulled away to go a set up.
The second took a similar course and Keys double-faulted on the first match point to gift Sabalenka victory in 65 minutes.
Sabalenka is on a collision course in the semi-finals with China's Olympic champion Qinwen Zheng, who faces 43rd-ranked Amanda Anisimova in the last 16 later Wednesday.
Three-time Grand Slam champion Sabalenka can take a major step towards overhauling Iga Swiatek at the top of the rankings by lifting the title in Beijing.
Swiatek is not playing in the Chinese capital because of "personal matters".
