Objective To investigated the common cancer patients' nutritional status, and to discuss the effect of malnutrition on the clinical outcome of patients. Methods 176 new admitted patients with malignant tumor were selected from March 2013 to April 2016. Patients' nutritional status was assessed by PG-SGA within 48 hours of admission, in the same time, the occurrence of infectious complications during the hospital, the hospital stay, the hospitalization expenses, non-planed 30 days re-admission and the death time or the survival time of the patients were recorded. Results In 176 patients, malnutrition incidence was 71.60%; The incidence of infectious complications in patients with malnutrition was 42.06%, which were higher than that in the patients with well nourished (6.00%). The malnutrition group had higher hospitalization expenses and longer hospital stay than the well nutrition group. The rate of non-planed 30 days re-admission in the patients with well-nourished (0) was significantly lower than those with malnutrition (9.52%). The poorer the nutritional status was, the shorter the survival time was. Conclusions The overall rate of malnutrition in common tumor patients were high. The malnutrition will directly affect the patient's clinical outcome, resulting in the higher incidence rate of infectious complications during the hospital, the longer hospital stay, the higher hospitalization expenses, incidence of the higher non-planed 30 days re-admission and the shorter survival time. Malnutrition is one of the independent risk factors that affect the planned 30-day hospitalization and survival.