Objective To measure the body compositions and their changes of peritoneal dialysis(PD)patients by multifrequency bioelectrical impedance analysis(MBIA)and compare the relative data with the peritoneal dialysis adequacy(Kt/V).Methods A total of 60 PD patients were divided into three groups according to body mass index(BMI):underweight group(BMI18.5),normal weight group(BMI18.5-23.9),and overweight and obese group(BMI≥23.9).The patients' weight(WT),body mass index(BMI),total body water(TBW),extracellular water(ECW),intracellular water(ICW),fat mass(FM),and fat-free mass(FFM)were measured by MBIA.Urea clearance rate(Kt/V)was estimated at the same time.Linear correlation were used to analysis between Kt/V and body composition indicators.Results Body composition indicators were significantly higher in overweight and obese group than in normal weight group(P0.05 or P0.01),and were significantly lower in underweight group than in normal weight group(P0.05 or P0.01).The Kt/V was significantly lower in overweight group than in normal weight group(P0.01).Kt/V was negatively correlated with TBW、ECW、ECW/TBW、ECW/ICW(P0.01).Conclusion Body composition is obviously different in PD patients with different BMI.MBIA appears to be a practical method for assessing fluid status and dialysis adequacy in PD patients.