Objective:To investigate the changes of serum anti-CRP autoantibodies(CRP-Ab) and their relationship in acute coronary syndrome (ACS) patients. Methods:Serum samples were taken from all patients with ACS(n=120),stable angina pain (SAP)(n=61) and subjects without coronary heart disease (NCAD) (n=120)subjects. The serum levels of CRP-Ab(IgG)were quantitatively measured by indirect ELISA assay. Absorbance(A) was measured at 405 nm. Positive cut-off values were calculated from the 95 th percentile of the A values in NCAD subjects. Results:The serum levels of CRP-Ab were greatly elevated in patients with ACS(1.75±1.09) compared with SAP(1.27±0.6.1) and NCAD(0.875±0.43) subjectes (P < 0.01,respectively). The positive tatio of CRP-Ab in ACS group(44.17%) are higher than SAP group(8.84%) (P < 0.001). There was no significant correlation between the serum level of CRP-Ab and the number of lesioned artery of coronary artery stenosis (P > 0.05). Conclusion:we found that autoantibodies to CRP are common in sera from patients with ACS. It is likely that this explains the relative of CRP response in patients with ACS.It can be excluded that anti-CRP autoantibodies have biological potentials of pathophysiological interest in ACS.