Objective To observe the feasibility of replacing creatinine clearance (Ccr) with Cystatin C (Cys C) as an endogenous marker of glomerular filtration rate(GFR). Methods Urine samples of 120 patients were collected and the concentration of creatinine were measured to calculate Ccr. At the same time, levels of serum Cys C were measured. One hundred and twenty patients were divided into 3 groups according to the different value of Ccr，which was compared with Cys C in each group. Results There was no significant difference between Cys C and Ccr in each group and they are well correlated (r>0.90). Conclusion Cys C as an endogenous marker of GFR is superior to Ccr, and testing serum Cys C is not only unnecessary to collect urine sample in methodology but also is accurate in results. It is feasible that Ccr is replaced by Cys C in routine clinical use.