Abstract： Objective To study the clinical value of Cys-C and MDRD equation in the patient with CKD.GFR was estimated by Cys-C and MDRD equation.To study the correlation between Cys-C and MDRD equation.Methods According to the value of GFR of the patient with CKD,divided them into five groups.To study the correlation between Cys-C and GFR.To explore the correlation between Cys-C and Sc.Results Cys-C was correlated with Scr.There was negative correlation between Cys-C and GFR.When renal function slightly injured,Cys-C was higher sensitivity than Scr.Conclusion It is reliable to detect Cys-C by enzyme linked immunosorbent assay(ELISA).It is dependable to judge renal function by the level of Cys-C.Cys-C can be a sensitive marker to reflect GFR.GFR was estimated by Cys-C and MDRD equation.It was correlation between Cys-C and MDRD equation.