Abstract: Objective To evaluate the efficiency and safety of olanzapine in acute and delayed chemotherapy-induced nausea and vomiting （CINV） among Chinese cancer patients who received highly emetogenic chemotherapy. Methods This experiment was designed as a randomized， self-crossover and blank control clinical trial. Two sequential cycles of highly emetogenic chemotherapy were carried out on 52 cases of malignant tumor patients who met the inclusion criterion. All the patients received a sequential A／B or B／A chemotherapy cycle randomly. In cycle A （blank control group）， each patient should receive the standard anti-nausea treatment by intravenous injection 30 minutes before chemotherapy， including palonosetron （0.25 mg， d1） and dexamethasone （10 mg， d1-d3）. In chemotherapy cycle B （olanzapine group）， patients not only received standard anti-nausea treatment like cycle A， but also a additional olanzapine treatment （10 mg po, qn） from the day before chemotherapy to the fifth day after chemotherapy administration. The primary endpoint in this study was the complete control rate of the nausea and vomiting happened within 5 days after chemotherapy administration， and the second endpoint was the safety of anti-nausea treatment. Results A total of 50 patients could be evaluated who fulfilled two different cycles of chemotherapy， and another 2 patients dropped out. When compared with non-olanzapine group， olanzapine group had a higher complete control rate of acute nausea （88.0％ vs. 52.0％， P＜0.05）， delayed nausea （72.0％ vs. 20.0％， P＜0.05）， and delayed vomiting （86.0％ vs. 64.0％， P＜0.05）. However， olanzapine group and non-olanzapine group both had a high complete control rate of acute vomiting （94.0％ vs. 86.0％）， but there was no significant difference（P＞0.05）. The main adverse effects suffered by patient in this trial included dizziness， somnolence， dry mouth， fatigue， constipation and orthostatic hypotension. The proportion and degree of adverse effect in olanzapine group and non-olanzapine group were very low， and there was no significant statistical difference between two groups（P＞0.05）. Conclusion Olanzapine can further improve the control efficiency of CINV based on the standard treatment of palonosetron and dexamethasone without increasing the adverse effect of treatment.