Objective To discuss the antineoplastic effect of rich selenium of amino acid of silkworm chrysalis on S180 tumor bearing mice. Methods The models of tumor bearing mice were established by hypodermic inoculating fifty Kunming healthy mice's right armpit.The mice were randomly divided into 5 groups next day according to the sex and body weight: tumor control group(0.9% sodium chloride injection),positive control group(CTX 0.03mg/g),high dosage of rich selenium of amino acid of silkworm chrysalis group(0.2mg/g),middle dosage group(0.1mg/g),low dosage group(0.05mg/g).Successive medication to mice for ten days.The next day,we got blood by pick eyeball of mice,and determine its leukocyte number and platelet number.We measured the weight of tumor and calculated the ratio of tumor restriction.The ratio of liver and body weight,spleen and body weight,lung and body weight and the change of weight after medication were observed. Results Compared to tumor control group,the weight of high dosage group middle dosage group and low dosage group were grown down obviously,the ratio of tumor restriction were 30.06%,25.43% and 22.54%.The leukocyte number and platelet number of positive group was lower than tumor group(F= 4.27,5.33,all P 0.05),and had statistical significance with positive group(F= 4.85,5.02,5.37,all P 0.05).Compared to tumor control group,the ratio of liver and body weight of high dosage group was lower(F= 6.31,P 0.05); the ratio of liver and body weight of middle dosage group was lower(F= 4.11,P 0.05);the ratio of liver and body weight,lung and body weight of low dosage group was lower(F= 3.83,4.54,all P 0.05).The ratio of liver and body weight,spleen and body weight,lung and body weight between rich selenium of amino acid of silkworm chrysalis and positive control group had statistics significance(P< 0.05). Conclusion Amino acid of silkworm chrysalis could inhibit the growth of S180 tumor.Though the antineoplastic effect of rich selenium of amino acid of silkworm chrysalis was not as good as CTX,its toxicity was lower than CTX.It has application value. Key words: Amino acid; S180 tumor bearing mice; Antineoplastic effect