Abstract: Objective To explore the value of plasminogen activator inhibitor-1 (PAI-1)in differential diagnosis of stable angina and unstable angina.Methods Clinical materials of 178 pa-tients with angina were analyzed retrospectively,and they were divided into Observation group (unsta-ble angina,n =87)and control group (stable angina,n =91)according to type of angina.Results Levels of CRP and PAI-1 in the observation group were significantly lower than those in the control group (P <0.001).There was a significant positive correlation between CRP and PAI-1 (r =0.189, P =0.012)in patients with angina.ROC analysis showed PAI-1 was able to differentiate unstable an-gina and stable angina with a cut-off value of 109.5 mg/L,a AUC of 0.947,a sensibility of 90.91%and a specificity of 91.11%.Conclusion Unstable angina patients have a higher level of PAI-1 than stable angina patients.PAI-1 can be used to differentiate unstable angina and stable angina.