Aim To observe the correlation of serum cystatin C, high-sensitive C-reactive protein (hs-CRP) level and virtual histology-intravascular ultrasound characteristics of culprit vessels in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). Methods 114 patients were divided into two groups according to the clinical characteristics:NSTE-ACS group and SAP group, 70 patients with NSTE-ACS, 44 patients with SAP. All patients underwent coronary angiography and virtual histology-intravascular ultrasound. Serum levels of cystatin C and hs-CRP were measured respectively. Culprit vessels were identified by comprehensive assessment including ST-T changes of ECG, ventricular wall motion abnormality of ultrasound examination and the complex lesion diagnosed by coronary angiography. A quantitative estimation with virtual histology intravascular ultrasound of all 70 culprit lesions in NSTE-ACS group and all 44 culprit lesions in SAP group. Then their correlations were analyzed. Results ①The serum levels of cystatin C and hs-CRP were significantly higher in NSTE-ACS group than those of SAP group(all P<0.01). ②The plaque burden, plaque area and necrotic core percentage of culprit lesions in NSTE-ACS group was significantly higher than those of SAP group (P<0.05 or P<0.01). ③Correlation analysis showed that, the serum level of cystatin C was positively correlated with hs-CRP and necrotic core percentage (r=0.634 and 0.602, all P<0.01), and was negatively correlated with HDLC (r=－0.466, P<0.01). The serum level of hs-CRP was positively correlated with plaque burden and plaque area (r=0.454 and 0.427, P<0.01 or P<0.05). Conclusions The serum cystatin C level is significantly increased in patients with NSTE-ACS, and it was associated with unstable composition of necrotic core of culprit vessels. The serum cystatin C level can be used for evaluating the stability of coronary lesions in patients with NSTE-ACS.