Objective Toinvestigate the relationship between red blood cell volume distribution width (RDW) and acute coronary syndrome (ACS),and the correlation between RDW and degree of coronary artery stenosis. Methods A total of 221patients accepting coronary angiography were involved as ACS group and another 50 patients also accepting coronary angiography as normal control group. ACS group wasfurther divided into unstable angina (UA) group of 77 cases and acute myocardial infarction (AMI) group of 144 cases ,then their level of RDW was detected. According to Gensini score ,we divided the 221 positive cases of coronary angiography into ≤ 30 point group ,31-60 point group and > 60 point group and their level of RDW was detected. Results The level of RDW in ACS group(13.02 ± 0.68)was significantly higher than that innormal control group(12.62 ± 0.38),and the difference was statisticallysignificant(P < 0.05). And the difference between UA group(12.84 ± 0.68)and AMI group(13.12 ± 0.66)also showed statistical significance(P < 0.05). With the increase of Gensini score ,the level of RDW was also increased ,and the difference between each two groups was statistically significant (P < 0.05) except that between control group and ≤ 30 point group. Conclusions The level of RDW in ACS group and AMI group is significantly higher ,suggesting that RDW may be involved in the pathogenesis of acute coronary syndrome ,and the RDW level could be a potential indicator of ACS. RDW level is closely related to the severity of coronary stenosis and could be one of its predictors.