Abstract: ObjectiveTo investigate the risk factors related to breast cancer and the potential interaction between the factors.MethodsA case-control study with 223 newly diagnosed female breast cancer patients and 322 healthy controls was conducted and unconditional Logistic regression was used to evaluate the risk.ResultsEarly age atmenarche(EAM), late age at first and last pregnancy (LAFP and LALP),dysmenorrheal could increase breast cancer risk with adjusted ORs (95% CI) of 1.79(1.26-2.55),1.56(1.10-2.20),1.49(1.04-2.15),1.88(1.22-2.90),respectively.Lactation could decrease breast cancer risk.There were combined effects between EAM and LAFP, EAM and LALP, EAM and not drinking tea,LAFP and not drinking tea, LALP and not drinking tea, family history of breast cancer and not drinking tea (P_trend<0.01).There were multiple interaction between EAM and not drinking tea LAFP and not drinking tea (P_int=0.029 and 0.000).ConclusionEAM,LAFP and LALP were risk factors of breast cancer, whereas, drinking tea may decrease the risk of breast cancer.Not drinking tea combined with EAM,LAFP,LALP could increase breast cancer risk greatly.