OBJECTIVE：To investigate the activity of lycorine to the in vivo apoptosis of tumor cells in H 22-bearing mice and its mechanism. METHODS ：Kunming mice were inoculated subcutaneously with ascites of H 22 hepatoma mice in the armpit of forelimb to establish solid tumor model. After modeling ，mice were randomly divided into negative control group ，positive control group（hydroxycamptothecin 6 mg/kg），lycorine low-dose ，medium-dose and high-dose groups （10，20，40 mg/kg），with 10 mice in each group. Negative control group was given constant volume of normal saline intragastrically ，and administration groups were given relevant medicine intragastrically ，once a day ，for consecutive 7 days. After last medication ，the weight of tumor was detected and anti-tumor rate was calculated. Ascites tumor model of mice was established by intraperitoneal injection of H 22 hepatoma mice ascites ，and then were grouped with same method and given relevant medicine as above. After last medication ， survival time of mice was recorded and the life prolongation rate was calculated. The early apoptotic rate of tumor cells in mice was detected by flow cytometry. On the basis of normal control group （normal mice without tumor ），the mitochondrial membrane permeability of tumor cells in each group was investigated by Calcein AM staining. The changes of mitochondrial potential were investigated by Rhodamine 123 staining. Colorimetry and Western blot assay were adopted to detect the Caspase-3 activity and expression of apoptosis-related protein （Bcl-2，Bax，Cyt-C and Caspase- 9）. RESULTS ：Compared with negative control UN- group，the tumor weight of positive control group and lycorine PYSCT-2017208） groups were decreased significantly ，while the survival time was significantly prolonged ，and the early apoptotic rate of tumor cells was significantly increased （P＜0.05 or P＜0.01）；the anti-tumor rates were 39.41％ ， 23.36％ ， 36.50％ ， 56.93％，and life prolonga tion rates were 49.23％，29.09％， E-mail：ym913@yahoo.com.cn 50.19％，69.08％. Compared with normal control group ，the mitochondrial membrane permeability ，Caspase-3 protein activity and protein expression of Cyt-C and Caspase- 9 were significantly increased，while the mitochondrial membrane potential and Bcl- 2/Bax ratio were decreased significantly （P＜0.05 or P＜0.01）. Compared with negative control group ，mitochondrial membrane permeability and Bcl- 2/Bax ratio were decreased significantly in administration groups ，while mitochondrial permeability ，Caspase-3 protein activity and protein expression of Cyt-C and Caspase- 9 were significantly increased （P＜0.05 or P＜0.01）. CONCLUSIONS ：Lycorine can induce the apoptosis of tumor cells in H22-bearing mice ，the effects of which may be associated with opening mitochondrial membrane permeability transition pore to increase mitochondrial permeability ， decreasing mitochondrial membrane potential and up-regulating the expression of apoptosis-related proteins.