Objective To investigate the correlation between red blood cell distribution width(RDW) and in-stent restenosis(ISR)in patients with coronary heart disease after PCI.Methods A total of nine hundred and seventy-eight patients with coronary heart disease treated in Beijing Anzhen Hospital,Capital Medical University with DES stent implantation from March 2015 to March 2016 were enrolled in the study.Among them,493 patients(50.41%)underwent coronary angiography in the hospital at 6-12 months after the operation.According to the results of the angiography,the patients were divided into two groups: the ISR group and the non-ISR group.The basic data of the patients,the laboratory indexes and the coronary interventional procedures record were collected to analyze the factors that could lead to in-stent restenosis.Results 51 cases(10.34%)in the ISR group and 442 cases(89.66%)in the non-ISR group.The baseline characteristics of the two groups were similar,and there was no significant difference in gender,age, body mass index,combined with hypertension,family history of coronary heart disease,long-term administration of statin and follow-up interval(P>0.05).The proportion of patients with diabetes was significantly higher than that of the non-ISR group(37.3% vs.22.6%,P=0.021);the smoking rate was significantly higher in the ISR group(52.9% vs.35.7%,P=0.016).In terms of laboratory examination,there were no significant differences between the two groups in blood lipid levels and WBC,RBC,Hb and PLT counts between the two groups(P>0.05).The levels of serum RDW(13.4(13.00,13.80)vs.12.7(12.40,13.10),P<0.01)and hs-CRP (3.15(2.32,4.63)vs.1.33(0.63,3.16),P<0.01)were significantly increased in the patients with ISR.The stent length was longer in the ISR group((21.87 ± 5.20)mm vs.(19.14 ± 4.87)mm,P<0.01),the stent diameter was smaller((2.87±0.38)mm vs.(3.09±0.36)mm,P<0.01),the number of cases with serial stents in ISR group was higher than that in non-ISR group(45.1 % Vs 30.8%,P=0.038).Multivariate logistic regression analysis showed that RDW(OR=2.396,95%CI 1.655-3.471;P<0.01),hs-CRP(OR=1.052, 95%CI:1.001-1.105;P=0.044),DM(OR=2.029,95%CI:1.004-4.100;P=0.049),smoking(OR=2.252,95%CI:1.060-4.783;P=0.035),stent length(OR=1.149,95%CI:1.072-1.230;P<0.01),stent diameter(OR=0.210,95%CI:0.079-0.558;P=0.002)and serial stents(OR=2.306,95%CI:1.162-4.575;P=0.017)were independent risk factors for in-stent restenosis.Conclusion Red blood cell distribution width is an independent predictor of in-stent restenosis after PCI in patients with coronary heart disease.Chronic inflammation and oxidative stress may be the most important pathogenesis of ISR.