Objective To investigate the effects of Casticin (CAS) on the growth of human cervical carcinoma HeLa cells xenografts in nude mice and its possible molecular mechanism. Methods Models of human cervical cancer HeLa cells xenografts transplanted subcutaneously in nude mice were established and randomly divided into five groups(each group including five nude mice): saline group, Cisplatin group, low dose CAS group, middle dose CAS group and high dose CAS group. Tumor volume and tumor weight were observed and compared. The alteration of the weight of nude mice, and the change of serum levels of LDH, ALT, Cr and WBC counts were examined and compared. The rate of apoptotic cells of human cervical carcinoma HeLa cells xenografts was analyzed by PI stained FCM. The expressions of cyclin B1 protein and p21 protein of HeLa cells xenografts were determined by western blot. Results CAS could significantly suppress the increasing volume and weight of human cervical carcinoma HeLa cells xenografts in nude mice models in time and dose dependent manner, yet had no significant effect on the weight of nude mice, the serum levels of LDH, ALT, Cr and WBC counts. When the xenografts cells treated with CAS for 16 days, the apoptotic rate of xenografts cells increased in a dose-dependent manner, and the expression of p21 protein was up-regulated and protein level of cyclin B1 was decreased. Conclusions CAS could suppress the growth of human cervical carcinoma HeLa cells xenografts in nude mice, which may be related to its promotion on xenografts cell apoptosis through down-regulation of cyclin B1 expression and activation of p21 expression.