Objective To study the nutrition and serum leptin level in maintenance hemodialysis patients of different dialysis modalities. Metheds 65 patients who started renal replacement therapy on HD or HD/HDF between 1997 and 2002 were considered. 40 patients were treated with HD, the other 25 patients with HD/HDF(HD and HDF once a month). The serum Alb, PA, BUN, leptin were measured. The serum leptin concentration of HD/HDF patients were compared with those of HD patients and control human-beings. Clearance and reduction rate of leptin were analyzed, and the correlation between leptin and other nutrition index were evaluated. Results Leptin level was significant higher in female patients than in male patients of group HD、HD/HDF and control group. Serum leptin level was significant lower after HDF, but not after HD. Serum leptin concentrition of HD/HDF patients was higher than that of HD patients,controlled human-being. Clearance and reduction rate of leptin group HDF were significant greater than that in group HD. Nutrition status, dosage of blood transfusion and erythropoietin of group HD/HDF are better than that of group HD. Serum leptin level showed significant positive correlation with BMI and PAB in all patients. Conclusion On-line HDF can clear part of leptin but HD can not.The elevated serum leptin concentrition of HD/HDF patients may due to improved nutrition status.