Patients undergoing peritoneal dialysis (PD) generally have malnutrition, which is the main reason for low survival, high hospitalization rate, and high mortality rate. The reasons for malnutrition are complex, including inflammation, inadequate dialysis, protein and calorie intake insufficiency, protein loss in the process of dialysis, high peritoneal transport, residual renal function (RRF) decline, chronic acidosis, high catabolism, and complications, that are all involved in the development and progression of malnutrition of PD patients. Malnutrition assessment requires a comprehensive judgement through a combination of history and examination indicators, such as subjective global assessment (SGA), protein nitrogen appearance rate (PNA), biochemical indicators, dual energy x-ray absorptiometry (DEXA), and bioimpedance analysis (BIA). It requires various comprehensive management to improve malnutrition in PD patients, including managing dietary intake, maintainning adequate dialysis dose, protecting RRF, and correcting acidosis; at the same time, attention should be paid to active prevention and treatment of peritonitis, maintainning the best balance of body fluids, using dialysate with good biocompatibility, and using drugs.