Abstract: Using the method of sanwich ELISA,we study the mean levels of serum SIL-2R in the patients with breast cancer.At the same time,we also detect 30 patiants with breast benign diease and 40 of norma lindividuals.The result shows that the serum SIL-2R of breast cancer much higher than that of breast benign diease and the controls (P<0.01).Serum SIL-2R level decrease significantg at 20 days after radical surgery for breast cancer,with no remarkably difference to the healthy (P>0.05)but the serum SIL-2R of 7 days after radical surgery for breast cancer similer that of pre-operater.The serum SIL-2R leavel in relative to the clinical stage of berast cacer,butisnt relative to the pathology.It can be concluded that serum SIL-2R assay is a new biological marker for the assessmert of the stage,the sponre to medical intervention and the prognosis in breast cancer.