Aim To investigate the changes of circulating endothelial cells (CEC), nitric oxide (NO), oxidized low density lipoprotein (ox-LDL), high-sensitivity C-reactive protein (Hs-CRP) and manifestation of acute coronary syndrome (ACS). Methods The plasma Hs-CRP levels were measured by using particle enhanced immunonephelometry and the plasma ox-LDL levels were measured by enzyme linked immunosorbent assay (ELISA) in 20 normal control subjects and 51 patients with ACS. The plasma CEC and NO levels were also determined. The linear correlation was analyzed to estimate the changes of these variables. Results The levels of ox-LDL, Hs-CRP, CEC in ACS patients were markedly higher than those in control group respectively (686±168 μg/L vs 349±172 μg/L, p<0.01), (6.15±1.75 mg/L vs 1.53±1.64 mg/L, p<0.01), [(8.9± 1.6) ×10~6 cells/L vs (2.4±0.4) ×10~6 cells/L, p<0.01]. The level of NO in ACS patients was significantly decreased compared with control group (52.2±16.5 μmol/L vs 77.3±21.0 μmol/L, p<0.05). The linear correlation analysis showed that the level of ox-LDL was correlated positively with CEC (r=0.781, p<0.001), and NO (r=0.792, p<0.001) in patients with ACS. The level of Hs-CRP was correlated positively with CEC (r=0.776, p<0.001) and NO (r=0.897, p<0.001) in patients with ACS. The level of ox-LDL was also positively correlated with CRP in patients with ACS (r=0.768, p<0.001). Furthermore, the level of CEC was positively correlated with NO in patients with ACS (r= 0.951 , p<0.001). Conclusion Ox-LDL and CRP may participate in endothelial dysfunction, which contributes to pathogenesis of ACS.