Objective To investigate the changes and clinical significance of red blood cell distribution width(RDW)in peripheral blood of patients with adenomyosis.Methods A retrospective study was performed on 300 adenomyosis patients and 250 age-matched individuals who were admitted to the Maternal & Child Health Hospital of Guangxi Zhuang Autonomous Region from January 2020 to December 2022.Mann-Whitney U test was used to compare blood parameters between the patient group(including before and after treatment)and the healthy control group.The diagnostic efficacy of RDW in adenomyosis was evaluated by ROC.Spearman correlation method was used to analyze RDW's association with other blood inflammatory parameters.Logistic multivariate analysis was applied to analyze the independent risk factors for adenomyosis.Results Compared with healthy control group,RDW values were in patients with adenomyosis[14.60％(13.20％～18.65％)vs 13.00％(12.40％～13.80)％],and the difference was statistically significant(Z=11.396,P=0.001).In addition,the RDW levels of patients after treatment were reduced compared with healthy control group[14.10％(12.10％～15.90％)vs 14.60％(13.20％～18.65％)],and the difference was statistically significant(Z=8.339,P=0.001).Correlation analysis results showed that RDW was negatively correlated with hemoglobin,hematocrit,mean corpuscular volume and absolute lymphocyte count(r=-0.709,-0.614,-0.801,-0.131,all P＜0.05),but positively correlated with red blood cell,platelet and platelet lymphocyte ratio(r=0.184,0.439,0.406,all P＜0.05).ROC curve analysis showed that the sensitivity and specificity of RDW for diagnosing adenomyosis were 63.0％and 97.6％,the area under the curve was 0.782,95％confidence interval was 0.745～0.819,respectively.Logistic regression analysis showed that RDW was independently associated with adenomyosis(OR=0.755,95％CI=0.677～1.347,P=0.012).Conclusion RDW was elevated in patients with adenomyosis,suggesting that RDW may be a potential auxiliary diagnostic marker for adenomyosis.