120 patients with malignant tumors diagnosed by pathology or cytology and treated with highly emetogenic chemotherapy drugs containing cisplatin from September 2018 to December 2019 were selected. The patients were randomly assigned to megestrol group (megestrol acetate dispersible tablets+5-HT3 receptor antagonist+dexamethasone) or control group (5-HT3 receptor antagonist + dexamethasone) at 1:1. The dosage of antiemetic drugs in the control group: 5-HT3 receptor antagonist 2.5mg, dexamethasone 12mg on the first day, 8mg on the 2nd-4th day, all were injected intravenously with 30min before chemotherapy for 5 days. The patients in the megestrol acetate group were given megestrol acetate dispersible tablets on the basis of the control group. 160 mg of megestrol acetate dispersible tablets were taken orally every morning on the day of the beginning of chemotherapy for 10 days. The main end point was the proportion of control of nausea and vomiting between the two groups during the delayed period (24-120 hours after the beginning of chemotherapy), that is, the proportion of complete remission (no vomiting and no need for rescue treatment) and complete prevention (no nausea and vomiting).The secondary end point was the control ratio of nausea and vomiting in the acute phase (0-24 hours after the beginning of chemotherapy) and the overall phase (0-120 hours after the beginning of chemotherapy); the proportion of patients with grade 3-4 nausea and vomiting during chemotherapy; the adverse reactions related to antiemetic drugs and the score of quality of life of patients in both groups before and after treatment.