OBJECTIVE： To provide reference for rational use of antiemetics in cancer patients. METHODS： Two thousand six hundred and sixteen pieces of medical orders of patients receiving antiemetics were collected from oncology department of our hospital via EMRS during Oct. 2015-Jun. 2016. RESULTS： Among 2 616 cases surveyed， 1 301 cases conformed to inclusion and exclusion criteria， of which irrational use of drugs were found in 595 cases， 760 times in total. Main manifestations were unsuitable drug selection （33.82％）， irrational usage and dosage （25.26％）， unsuitable drug combination （34.08％） and non-standard medication course （6.84％）. The incidence of nausea in female was higher than male， with statistical sighificance （P＝0.003）， but gender had no significant effect on the incidence of nausea （P＞0.05）. Age had no significant effect on both nausea and vomiting （P＞0.05）. The control rate of nausea/vomiting in rational drug use group was higher than irrational drug use group. Average cost of antiemetic treatment of different emetic risk chemotherapy drugs in rational drug use group were all lower than irrational drug use group， indicating therapeutic efficacy could be guaranteed and economic burden was reduced in rational drug use group. CONCLUSIONS： The antiemetic plan should be selected rationally according to emetic risk degree of chemotherapy drugs. Patients receiving combined chemotherapy should select antiemetic plan according to highest emetic risk degree of chemotherapy drugs， and strictly master usage， dosage and duration. At the same time， treatment cost should be considered when selecting antiemetic plan to guarantee the safe， effective， economical and rational use of drugs.