To investigate the risk factors of renal anemia in maintenance hemodialysis (MHD) patients and the association of neutrophil / lymphocyte ratio (NLR) level with renal anemia. Methods 140 patients who underwent MHD in the blood purification center of The Affiliated Hospital of Southwest Medical University from January 2020 to January 2021 were selected and divided into anemia group and non anemia group according to the level of hemoglobin (HB). The general data, hemoglobin (HB), neutrophil absolute value (NEU), lymphocyte absolute value (LYM), ferritin (FER), folic acid (FA), vitamin B12 (VitB12), albumin (ALB), C-reactive protein (CRP), serum amyloid A (SAA),β2 microglobulin(β2-MG) and other laboratory indexes were collected. Pearson / Spearman method was used to analyze the correlation between anemia and blood neutrophil / lymphocyte ratio and the above indexes. Logistic regression method was used to analyze the risk factors of renal anemia, and ROC curve was used to analyze the predictive value of neutrophil / lymphocyte ratio for anemia. Results 140 patients with MHD were included, including 71 cases (50.7%) in anemia group and 69 cases (49.3%) in non anemia group. The levels of neutrophil / lymphocyte ratio and neutrophil absolute value in anemia group were significantly higher than that in non anemia group (P＜0.05), while the levels of LYM、ALB and 25-(OH)-VitD3 were lower than that in non anemia group (P＜0.05). There was no difference in age, dialysis age, gender, complications (hypertension, diabetes), Weekly erythropoietin dosage, BMI, FER, FA, VitB12, CRP, SAA, β2-MG, Ca2+, P and iPTH between the two groups (P＞0.05). Correlation analysis showed that Hb level was negatively correlated with NLR (r=-0.434)and CRP (r=- 0.178), and positively correlated with ALB (r=0.183) 、25-(OH)-VitD3 (r=0.243) and LYM(r=0.305) (all P＜0.05). Logistic regression analysis showed that low blood 25-(OH)-VitD3 level and high NLR level were independent risk factors for anemia in MHD patients. ROC curve analysis showed that the area under the curve (AUC) of NLR for predicting anemia in MHD patients was 0.802, the best diagnostic cut-off value was 3.563. The sensitivity was 0.831 and the specificity was 0.638. =Conclusion The increase of neutrophil / lymphocyte ratio in MHD patients is closely related to the decrease of hemoglobin level. Low blood 25-(OH)-VitD3 level and high NLR level are independent risk factors for renal anemia in MHD patients. NLR is expected to become a new index to assist in the diagnosis of anemia in MHD patients