Objective To establish the first national standard of Cystatin C.Methods The candidate standard was prepared from human recombinant Cystatin C,diluted and dispensed aseptically.Homogeneity and stability study were carried out on the automated biochemical analyzer.The target value was assigned by six laboratories using widely recognized immumoassay under strict conditions,and traceable to ERM-DA471.Commutabilities of the candidate standard and its saline dilutions were evaluated according to EP14-Evaluation of Matrix Effects.Excel 2007 was used to analyze the results.Results The preparation had good immunological activity and was proved to be homogeneous and stable (6 months sealed at 2-8 ℃,30 days sealed at room temperature and 37 ℃,30 days open-vial at 2-8 ℃).The assigned value of the preparation was (4.47 ± 0.25) mg/L (coverage factor k =2).The candidate standard and/or its saline dilutions have commutability on the 10 evaluated systems.Conclusion The preparation meets the requirements of national secondary standard and could be used in quality control and evaluation of Cystatin C assays in China.