Abstract: Objective To study the value of serum Cystatin C （Cyst-c） levels in detecting early renal damage in old hypertension patients. Methods Serum Cyst-c and creatinine （Cr） levels were determined in 412 old hypertension patients and compare with a control group（n=30）. Results Among 412 patients, there was early renal damage in 197 cases（47.82%）, renal failure in 24 cases（5.82%）, normal renal function in 191 cases（46.36%）. Serum Cyst-c levels in the early renal damage group was higher than the controlled group （2.34±0.8 and 0.9±0.2）mg/L, P＜0.01. There was no difference in serum Cr levels between the early renal damage group and the control group （86.6±12.7 and 81.0±10.5）μmol/L, P＞0.05. Conclusion Serum Cyst-c levels is a sensitive indicator for detecting early renal damage which was not found by serum Cr.