The third-seeded Romanian converted four of her eight break-point opportunities to set up a 6-4 6-3 victory over the eighth seed.
Cirstea's opponent in the last four will be Britain's Laura Robson, who upset seventh seed Peng Shuai in an epic contest.
The pair were on court for a little over three hours before Robson, ranked 74 in the world, emerged a 7-5 5-7 6-2 victor.
The win continues Robson's remarkable success against Chinese opposition, having ousted Li Na in the US Open and second seed Zheng Zi here in Guangzhou.
The other semi-final will pit fourth seed Urszula Radwanska against Su-Wei Hsieh.
Radwanska beat Chantelle Scheepers of South Africa 6-1 7-5 in the last eight while Hsieh was a 6-3 6-0 winner over Frenchwoman Mathilde Johansson.