Objective To investigate the correlation between serum levels of Cystatin C and unstable angina (UA). Methods 147 cases of patients with unstable angina were selected as the observation group and divided into three sub groups according to Braunwald classification, 50 cases of non coronary heart disease patients as control group. The serum Cystatin C levels in these four groups were detected. Results The serum Cystatin C level and the positive rate in observation group were significantly higher than that of control group. The serum cystatin C levels and positive rate in Braunwald Ⅲ group patients were higher than that of Braunwald grade II and grade I group of patients, and the serum cystatin C levels in Braunwald grade II group were also higher than that of Braunwald Ⅰ group patients (P < 0.05). Conclusion The serum Cystatin C level in patients is increased with the increasing of unstable angina severity. The detection of serum Cystatin C has some predictive value and may be helpful in the diagnosis and guiding treatment of unstable angina severity.