Objective: The aim of the study was to investigate the effect of Casticin on proliferation inhibition of human cervical cancer HeLa cells in vitro and to unravel the associated mechanisms.Methods: Human cervical HeLa cells were cultured in vitro.The inhibitory effect of Casticin on the viability of human cervical cancer HeLa cells was evaluated by the MTT assay.The colony formation ability was detected by plate colony formation assay.Distribution of cell cycle was analyzed by flow cytometry.The protein expression levels were analyzed by Western blot.Results: Casticin significantly inhibited the growth of human cervical cancer HeLa cells in a doseand time-dependent manner,and the IC50 was 2.82 μg/mL.The colony-forming rate was reduced drastically compared with control group (P < 0.05).The cells were markedly arrested at G2/M phase after the treatment of Casticin for 48 h.Western blot showed that the expression of p21 protein was up-regulated and protein level of Cyclin B1 was depressed by Casticin in a concentration dependent manner.Conclusion: Casticin could inhibit the cell growth and lead to cell arrest in human cervical cancer HeLa cells,and the down-regulation of Cyclin B1 protein expression and activation of p21 protein might contribute to Casticin induced cell arrest in human cervical cancer HeLa cells. Objective: The aim of the study was to investigate the effect of Casticin on proliferation inhibition of human cervical cancer HeLa cells in vitro and to unravel the associated mechanisms. Methods: Human cervical HeLa cells were cultured in vitro. Inhibitory effect of Casticin on the viability of human cervical cancer HeLa cells was evaluated by the MTT assay. Distribution of cell cycle was analyzed by flow cytometry. The protein expression levels were analyzed by Western blot. Results: Casticin significantly inhibited the growth of human cervical cancer HeLa cells in a dose and time-dependent manner, and the IC50 was 2.82 μg / mL. The colony-forming rate was reduced drastically compared with control group (P <0.05). The cells were markedly arrested at G2 / M phase after the treatment of Casticin for 48 h. Western blot showed that the expression of p21 protein was up-regulated and protein level of Cyclin B1 was depressed by Casticin in a concentration dependent manner. Conlusion: Casticin could inhibit the cell growth and lead to cell arrest in human cervical cancer HeLa cells, and the down-regulation of Cyclin Bl protein expression and activation of p21 protein might contribute to Casticin induced cell arrest in human cervical cancer HeLa cells.