Objective：To detect the levels of serum biomarkers in acute coronary syndrome（ACS） patients and to explore the signifi－cance of the detection for evaluating carotid plaque stability. Methods：Totally 90 patients with ACS were selected from the car－diovascular department in our hospital during January 2016 and December 2017. The ACS patients were divided into the vulnerable plaque group（51 cases） and the stable plaque group（39 cases），according to the results of carotid ultrasonography. Forty-five healthy people，who without any carotid plaque were chosen as the control group. ELISA method was used to detect serum high-sensitivity C reactive protein（hs-CRP），pentraxin-3（PTX-3），pregnancy related protein-A（PAPP-A），lipoprotein related phospholipase A2（Lp-PLA2） and oxidized low density lipoprotein（ox-LDL） level in three groups. Results：The serum levels of all indicators in the observation group were significantly higher than those in the normal control group（P＜0.05）. The levels of serum PTX-3，PAPP-A，Lp-PLA2 and ox-LDL in vulnerable plaque group were significantly higher than those in stable plaque group（P＜0.05）. The OR value is be－tween 1.2 and 2. The results of ROC curve analysis showed that the area under the ROC curve（AUC） of PTX-3，PAPP-A，Lp-PLA2 and ox-LDL were 0.764，0.870，0.678 and 0.794，respec－tively，and the critical values were 4.38 μg/L，11.28 U/L，and 181.64 μg/L and 490.86 μg/L，respectively. The sensitivity was 62.7%，76.5%，51% and 92.2%，and the specificity was 92.3%，95%，84.6% and 56.4%，respectively. Conclusion：Elevated serum hs-CRP，PTX-3，PAPP-A，Lp-PLA2 and ox-LDL level is closely related to ACS carotid plaque instability. It can be used as a serolog－ical index to evaluate the stability of carotid plaques in ACS.