Objective To investigate the effect of vitamin E on progression of breast cancer tumor and to explore its underlying mechanism.Methods Human Breast cancer cells MCF-7 were inoculated into mice to establish mouse model of breast cancer and MCF-7 cell was cultured in vitro.Reactive oxygen species (ROS)level and p53 expression were determined by fluorescence probe CM-H2DCFDA and Western blot respectively.In addition,proliferation of human breast cancer cells MCF-7 was observed after transfected by siRNA targeting p53.Results Supplementing the diet with vitamin E markedly increased tumor progression and decreased ROS level and p53 expression in tumor tissue.Supplementing the culture medium with trolox significantly accelerated the growth of MCF-7 and decreased ROS level and p53 expression in tumor cells.p53-siRNA could eliminate p53 expression in MCF-7 and increase the proliferation of MCF-7 cells.Conclusion Vitamin E can accelerate breast cancer tumor progression by reducing ROS level and decreasing the expression of p53 in tumor cells.