The world number 50 is ranked some 372 places above her opponent, but she needed three sets in a back and forth 6-2 3-6 6-3 victory at the WTA 125k hard-court event in Nanchang.
Peng had already racked up a victory over Liu in Shenzhen this year and the seeming gulf in quality told in a first set in which the top seed broke twice and won 81 per cent of first-serve points.
However, Liu improved massively in the second set, the world number 422 firing down four aces and showing her tenacious qualities by fending off three break-point opportunities.
It was the first time all week that Peng had dropped a set and the decider proved an equally tense affair.
There were three breaks of serve, but Liu's service game began to falter and she landed just 38 per cent of first serves.
Subsequently, Peng had ample opportunity to attack and she duly wrapped up victory in a time of two hours and two minutes.