Background Rupture of unstable plaque with subsequent thrombus formation is the common pathophysiological substrate of the acute coronary syndrome (ACS). It is of potential significance to explore the blood indexes predicting plaque characteristics. Little studies have focused on this field. Therefore we investigated the relationship between hypersensitive C-reactive protein (hs-CRP), pro-matrix metalloproteinase-1 (proMMP-1),tissue inhibitors of matrix metalloproteinase-1 (TIMP-1) and coronary plaque morphology.Methods Intravascular ultrasound (IVUS) examination was done in 152 patients with confirmed coronary heart disease before percutaneous coronary intervention from February 2003 to July 2005. Plasma samples of arterial blood were collected prior to the procedure. The level of hs-CRP, proMMP-1 and TIMP-1 were respectively measured by enzyme-linked immunosorbent assay (ELISA).Results Unstable and ruptured plaque were found more frequently in patients with acute myocardial infarction and unstable angina. Extal elastic membrane cross-sectional area (EEM CSA), plaque area, lipid pool area and plaque burden were significantly larger in ruptured and unstable plaque group. Positive remolding, thinner frequent in ruptured and unstable plaque group. The levels of plasma hs-CRP, proMMP-1 and TIMP-1 were higher in ruptured plaque group. hs-CRP＞8.94 mg/L was used to predict ruptured plaque with a ROC curve area of 0.76 [95% confidence interval (CI), 67.0%-85.8%], sensitivity of 71.8%, specificity of 77.0% and accuracy of 69.2% (P＜0.01), similarly for proMMP-1＞0.12 ng/ml with a ROC curve area of 0.69 [95% CI, 58.2%-80.2%], sensitivity of 69.2%, specificity of 75.2% and accuracy of 66.2% (P＜0.01), and TIMP-1＞83.45 ng/ml with a ROC curve area of 0.67 [95% CI, 56.2%-78.3%], sensitivity of 66.7%, specificity of 61.9% and accuracy of 66.2% (P＜0.01).Conclusion The plaque characteristics correlate with the clinical presentation. The elevation of hs-CRP,proMMP-1 and TIMP-1 are related to the plaque instability and rupture.