Objective: To investigate the association of red blood cell distribution width (RDW) to the treatment response in the newly diagnosed patients with chronic myeloid leukemia(CML) after 3 months、6months and 12 months of tyrosine kinase inhibitor(TKI ) treatment. Methods: A retrospective analysis of 175 newly diagnosed CML chronic phase patients who were treated in the First Affiliated Hospital of Nanjing Medical University from October 2010 to August 2021 in our hospital , all patients were treated with first-generation TKI (imatinib) or secend-generation TKI (nilotinib 、dasatinib and flumatinib) .According to the treatment response, they were divided into two groups: the optimal response group and the warning or treatment failure group, to analyze the influence of RDW and related clinical data on treatment response.The receiver operating characteristic (ROC) curve was used to optimize the cut-off values of clinical indicator. Results: Patients with RDW ≥ 16.15% at first diagnosed had significantly worse response (warnings and failures) to treatment at 3 and 6 months than those with lower RDW(P＜0.05). Analyzing the patients who did not achieve the best response after 3 months of TKI treatment and did not change the dressing early, Combined with the RDW at the first diagnosed, it was found that the treatment failure rate of the high RDW group at 6 or 12 months was significantly higher than that of the low RDW group(P＜0.05). Conclusion: RDW at the first diagnosis of CML-CP patients is an Independent predictor for early treatment response(3 and 6 months) of TKI. patients with high RDW and the 3-month efficacy evaluation is to warn are more likely to fail treatment at 6 and 12 months