Abstract: Objective observe the effects of hemodiafiltration (HDF) on phagocytic function of neutrophils, acid-base and electrolyte in uremic patients.Methods Twenty-nine uremic patients and 25 normal controls for general health examination in our hospital physical examination center were enrolled in this study. Uremic patients were treated with high flux hemodiafiltration once. In the process of HFHDF the average displacement liquid flow rate was 125 to 150 ml/min, the displacement liquid total of 30 to 40 L. The ultrafiltration volume was 2 to 4 L, with a blood flow of 350 to 400 ml/min and a dialysate flow of 500 to 600 ml/min, 4 hours per session. All patients receiving dialysis treatment were treated with fistula or long term indwelling catheter in the internal jugular vein, dialysate as bicarbonate dialysate, and low molecular weight heparin or unfractionated heparin was used for anticoagulation. Neutrophil phagocytic rate, neutrophil phagocytic index, blood urea nitrogen (BUN), creatinine (SCr), serum albumin, highsensitivity C-reactive protein (hs-CRP), β₂-microglobulin (MG), serum kalium (K⁺), serum sodium, serum chlorine, serum calcium, serum phosphate (P^-) and carbon dioxide-combining power (CO₂CP) were detected in uremic patients pre- and post-HFHDF. Neutrophil phagocytic rate, and phagocytic index were also assessed in control group. After 30 min of incubation of blood samples of both uremic patients and health controls with Staphylococcus albus, neutrophils were observed under a microscope, the neutrophil phagocytic rate and phagocytic index were calculated, and other items were tested in clinical laboratory of our hospital.Results Neutrophil phagocytic rate and phagocytic index of patients pre-HFHDF were lower than those of controls (P<0.05). Among 29 uremic patients, a significant increase of the neutrophil phagocytic rate was observed (P<0.05), while there was no statistically significant difference in neutrophil phagocytic index pre- and post-HFHDF (P>0.05). Neutrophil phagocytic rate, phagocytic index, CO₂CP and C3 of patients were significantly higher after the session, while the BUN, SCr, β₂-MG, K⁺, and P^- were significantly lower than those before (P<0.05). No statistically significant difference was observed in the level of hs-CRP pre- and post-session (P>0.05).Conclusions Phagocytic function of neutrophils is decreased in uremic patients. HFHDF can not only effectively remove uremic solutes, correct acid-base and electrolyte imbalance, but also enhance phagocytic capacity of neutrophils in uremic patients.