Aim To detect the levels of plasma oxidized low density lipoprotein (ox-LDL) and platelet aggregation in patients with acute coronary syndrome (ACS), and explore the effects of ox-LDL on the levels of platelet aggregation in patients with ACS. Methods A total of 158 patients with coronary heart disease (CHD) diagnosed by coronary angiography were enrolled in this study, including 48 patients with stable angina (SA), 59 patients with unstable angina (UA) and 51 patients with acute myocardial infarction (AMI). In addition, 60 hospital patients, chest pain without coronary artery stenosis, served as a control group. The levels of plasma ox-LDL were determined by ELISA, the levels of platelet aggregation were detected by turbidimetric aggregation monitoring device. Results Compared with control group, the levels of plasma ox-LDL and platelet aggregation were significantly increased in patients with UA and AMI, and there was no obvious change between control group and SA group, UA and AMI groups. In addition, the levels of plasma ox-LDL were positively correlated with the levels of platelet aggregation. Moreover, in vitro, ox-LDL could markedly promote ADP-induced platelet aggregation in patients with ACS. Conclusions Increased levels of plasma ox-LDL were associated with elevated levels of platelet aggregation in patients with ACS. Increased levels of plasma ox-LDL played a key factor role in the formation of atherothrombosis in patients with ACS, therefore, it was crucially important to detect the levels of ox-LDL in patients with ACS.