Savile battled past Germany's Anna-Lena Friedsam, ranked 63 places higher, 3-6, 6-3 6-1, in a match lasting more than two-and-half hours. Saville, the world No.177, will next meet top seed Magda Linette.
The competition is the first in China since the WTA launched a boycott in December 2021 after former top-20 player Peng Shuai said on social media that she had been sexually assaulted by a senior Communist Party official.
The post was subsequently deleted and Peng disappeared from view, later reappearing at a series of seemingly-staged events and interviews.
The WTA pushed for an investigation into her claims, but in April this year lifted the suspension, admitting, "the situation has shown no sign of changing".
Their statement added: "We have concluded we will never fully secure those goals, and it will be our players and tournaments who ultimately will be paying an extraordinary price for their sacrifices."
This is the first WTA competition in China since, and it is a quiet return with Polish world No.27 Linette the highest-ranked player. Only four players in the top 100 are in the event with No.48 Tatjana Maria the only other top-50 player.
The last time it was staged, in September 2019, there were seven top 50 players in the draw with three top-20 players including American winner Sofia Kenin. Australia's Sam Stosur was the beaten finalist in her last WTA singles final before retiring.
Maria also advanced to the last 16 on Tuesday, beating Philippine qualifier Alexandra Eala 6-3, 6-0.
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