Abstract: In this paper,the effects of low dose cyclophosphamide(CYT)on the tumor genenation growth in tumor-implanted mice were studied by using normal and tumor-implanted mice as models.We also investigated the effect of low dose CYT on tumor incidence,tumor weight and the free radical smetabolism.We found that D₁ can make the tumor incidence lower than that of tumor-implanted group,decrease the tumor weight,the SOD and GSH-Px of tumor-implanted mice liver was increased after pretreated by D₁,and MDA was tending to reduce.So low dose CYT can decrease the tumor incidence and tumor weight,increase the activity of SOD and GSH-PX.All of above prove that D₁ can affect tumor treating positively.And we should go further into the mechanism of D₁.