OBJECTIVE：To preliminarily study the antitumor mechanism of Periplaneta americana extract C Ⅱ-3 on MFC tumor-bearing mice. METHODS ：Balb/c mice were randomly divided into model group （normal saline 20 mL/kg）and C Ⅱ-3 group （200 mg/kg），with 6 mice in each group. MFC cell suspension （0.2 mL）was injected under the right armpit of mice. On the next day，mice were given relevant medicine intragastrically ，once a day ，for consecutive 10 d. 24 h after the last administration ，Based on the measurement of tumor size ， 1H-NMR technology combined with unsupervised PCA ，supervised PLS-DA and OPLS-DA were used to compare metabolic spectrum of liver tissue from tumor-bearing mice of 2 groups，to analyze differential metabolites and to explore the potential antitumor mechanis m of C Ⅱ -3. RESULTS ：Compared with model group ，the tumor body was significantly reduced in tumor-bearing mice of C Ⅱ-3 group. There were differences in 1H-NMR spectra between the 2 No.81960712）； groups. According to unsupervised PCA ，supervised PLS-DA and OPLS-DA ，totally six potential differential metabolites ，as glycogen （increased），pyruvate （decreased），arginine （de- creased），hydroxyproline （increased），inosine （increased） and niacinamide （increased），were identified in the liver tissue，which were mainly attributed to the metabolism of arginine ，energy and nucleic acid. CONCLUSIONS：The anti tumor effect of C Ⅱ-3 may be related to the regulation of arginine metabolism ，energy metabolism and nucleic acid metabolism.