Aim To investigate the relationship between the levels of pregnancy-associated plasma protein-A (PAPP-A) and high-sensitivity C-reactive protein (hs-CRP) in patients with unstable angina (UA), and the role of PAPP-A in predicting the stability of atherosclerotic plaques. Methods Patients were divided into two groups according to the clinic presentation, one with stable angina pectoris (SA group, n=38) and one with UA (UA group, n=42). The levels of PAPP-A, hs-CRP and other serum biomarkers were measured before coronary angiography; the angiograms were analyzed with Jenkins score. Results The plasma hs-CRP, PAPP-A levels in patients with UA increased significantly, compared with those in SA group (hs-CRP 4.40±0.003 vs 0.48±0.016 mg/L, p<0.001; PAPP-A 18.40±0.002 vs 7.79±0.001 mIU/L, p<0.001); the Jenkins scores of coronary artery angiography in patients with UA increased significantly compared with those in SA group (5.06±0.002 vs 1.94±0.002,p<0.001). PAPP-A was significantly related with hs-CRP (r=0.44); using the method of Multiple Regression and Correlation, PAPP-A had linear relationship with hs-CRP, cardiac troponin I (cTnI) in all of the cases, and Jenkins scores had linear relation with PAPP-A, cTnI and high density lipoprotein cholesterol. Conclusions PAPP-A can play a role in evaluating the clinic stability of the patients with coronary artery disease, and may act as one of the biomarkers of vulnerable plaques.