OBJECTIVE： To investigate anti-tumor effects of Periplaneta americana polypeptide PAP-2 on H22 tumor-bearing mice. METHODS： The mice tumor-bearing model was established by subcutaneous injection of ascites of H22 hepatocellular carcinoma mice via axilla. 70 mice were randomly divided into model group （normal saline）， 5-FU group （positive drug control， 20 mg/kg）， P. americana extract skimmed cream group （200 mg/kg， calculated by extract）， CⅡ-3 group （polypeptide isolated from skimmed cream as main active ingredient， 200 mg/kg， calculated by extract） and polypeptide PAP-2 high-dose， medium-dose and low-dose groups （isolated from CⅡ-3， 200， 100， 50 mg/kg， calculated by monomer）， with 10 mice in each group. The mice in the 5-FU group were given intraperitoneal injection once every other day， while the mice in the other groups were given intragastric administration once a day， the administration cycle was 10 d. After medication， the changes of tumor were observed and the organs （spleen， thymus and liver） index were measured. Histopathological changes of tumor tissue were observed after HE staining. The contents of VEGF， IL-1β and IL-4 in serum were determined by ELISA. RESULTS： Skimmed cream， CⅡ-3 and different doses of PAP-2 could inhibit the growth of tumor in tumor-bearing mice to different extent and increase organ index， and PAP-2 showed a dose-effect relationship. The tumor inhibition rate （38.95％） of PAP-2 high dose group was significantly higher than those of skimmed cream group and CⅡ-3 group （P＜0.05）， which was close to that （40.87％） of 5-FU group （P＞0.05）. Spleen index， thymus index and liver index of mice in PAP-2 high dose group were significantly those of model group and CⅡ-3 group （P＜0.05）； and the liver index of mice in PAP-2 high dose group was significantly higher than that of skimmed cream group （P＜0.05）. In addition， PAP-2 could decrease the serum contents of VEGF and IL-4， and increased serum content of IL-1β， with high dose group showed significant difference compared with model group （P＜0.05）； the serum content of IL-1β of mice in PAP-2 high dose group was significantly higher the that of skimmed cream group and CⅡ-3 group （P＜0.05）， serum contnet of IL-4 in PAP-2 high dose group was significantly lower the  that of skimmed cream group and CⅡ-3 group （P＜0.05）， but the serum content in which was significantly lower than that of skimmed cream group and CⅡ-3 group（P＜0.05）. CONCLU- SIONS： P. americana polypeptide PAP-2 it has a certern anti-tumor effects on H22 tumor-bearing mice， and its can increase the index of organs of H22 tumor-bearing mice， decrease the contents of VEGF and IL-4 in serum， increase the content of IL-1β in serum.