Objective:To investigate the role of soluble Fas ligand (sFasL) in the mechanism of immune escape and counterattack of colorectal cancer.Methods:ELISA was used to detect the level of sFasL in the sera of colorectal cancer patients and the supernatant of SW480. Transmission electron microscopy (TEM), flow cytometry (FCM) analysis and fluorescence microscopy were used to examine the apoptosis of Jurkat induced by the sera of colorectal cancer patients and the supernatant of SW480. The apoptosis was also studied after pretreatment of Jurkat by Fas blocking antibody ZB4. The supernatant of African green monkey cell line Vero was used as control.Results:The concentration of sFasL in sera of colorectal cancer patients was 12.21?1.14 ?g/L before treatment, the concentration decreased significantly after treatment(P