Cao Zheng, nicknamed the “Knife-Wielding Demon,” is a Liangshan hero in Water Margin. He once studied butchery and knife skills in the capital before drifting into the region around Yellow Mud Ridge, where he eventually operates an inn.
After losing the Birthday Gifts, Yang Zhi wanders through the martial world and comes into conflict with Cao Zheng at his establishment. The two fight, but Cao Zheng soon recognizes Yang Zhi’s ability and learns his identity, turning the confrontation into friendship.
Yang Zhi later attempts to seek refuge at Twin Dragons Mountain but finds that the stronghold’s leader, Deng Long, refuses to admit him. Cao Zheng helps devise a plan and establishes contact with Lu Zhishen. Together, they remove Deng Long and allow Lu Zhishen, Yang Zhi, and their allies to take control of the mountain.
When the Twin Dragons Mountain group is eventually absorbed into Liangshan, Cao Zheng joins the brotherhood and becomes one of the 108 heroes. He is not among Liangshan’s foremost warriors, but his role connects Yang Zhi, Lu Zhishen, and the expansion of the mountain strongholds into the larger Liangshan network.
