Objective To establish a tree shrew mode of breast tumor.Method Forty-five 3 to 4 month-old female tree shrews were orally gavaged with 20 mg 7,12-dimethylbenz(a)anthracene (DMBA) or peanut oil per animal for three times.Following that, fifteen DMBA administrated tree shrews were implanted 90 day-release medroxyprogesterone acetate ( MPA) pellets.The tree shrews were palpated once weekly to detect mammary tumors for 45 weeks after first DMBA administration.Results DMBA were able to induce breast tumors (12.5%) in tree shrews, and MPA increased the tumor incidence (50%) while no breast tumors were observed in the control group.Three induced breast tumors were intraductal papillary carcinomas and one was IDC by H&E stain.Conclusion All induced tumors are similar with spontaneous tumors in structure and molecular markers.