To explore the preventive effect of Prunus cerasifera Ehrh. fruit extract on obesity induced by high-fat diet in mice. The crude extract of fruit was obtained by water extraction， the content of polyphenol was determined by Folin phenol method， and the antioxidant activity was determined by DPPH. The mice were fed with high-fat diet and Prunus cerasifera Ehrh. fruit extract， and the weight of mice was measured every week， the relevant biochemical indexes in serum and liver were measured 10 weeks later， and the expression of liver lipid metabolism related genes was measured by real-time PCR. The results showed that the extract could significantly reduce the body weight of obese mice induced by high-fat diet， the contents of triglyceride （TG）， total cholesterol （T-CHO）， in serum and liver. Increase the content of superoxide dismutase （SOD） and reduce the contents of alkaline phosphatase （AKP）， aspartate aminotransferase （AST/GOT）， alanine aminotransferase（ALT / GPT） in serum. The expression of peroxisome proliferator activated receptor （PPARγ）， CCAAT / enhancer binding protein α （C / EBP α）， adipogenic transcription factor sterol regulatory element binding protein 1c （SREBP-1c）， lipid synthesis related genes （FAS） were significantly reduced. The results showed that Prunus cerasifera Ehrh. fruit extract could prevent obesity induced by high fat diet， improve the antioxidant activity of the body and protect the liver injury induced by high-fat diet.