Objective To study the value of RDW in severity evaluation and prognostic assessment of COPD. Methods Retrospective study was carried out on 115 COPD patients and 50 healthy controls. Blood routine, CRP, IL-6 data were collected on admission aiming at analyzing RDW difference in patients and controls, severity, severity grading and evaluation of prognosis. Results The level of CRP, RDW, IL-6 and WBC in patients were higher than that of healthy controls(P < 0.05). Mild and moderate groups have no significant difference from each other in terms of RDW, CRP and IL-6 conparison, but the difference between any other two groups were significant. There were significant positive correlation between RDW and CRP, IL-6, and negative correlations between the post-bronchodilator FEV1% and RDW. The mortality rate for patients with higher RDW level was higher than those with normal RDW. Conclusion Elevated RDW levels on admission are associated with severity of patients with COPD. RDW may be a prognostic marker for COPD.