OBJECTIVE：To systematically review the effectiveness and safety of olanzapine in the prevention and treatment of chemotherapy-induced nausea and vomiting （CINV）， and provide  evidence-based reference for clinical treatment. METHODS： Retrieved from Medline， PubMed， EMBase， Cochrane Library， Clinical Trials.gov， CBM， CJFD， VIP and Wanfang Database， randomized controlled trials （RCT） about olanzapine （test group） versus other drugs or conventional antiemetic regimen （control group） in the prevention and treatment of CINV were collected， Meta-analysis was performed by using Rev Man 5.3 software after data extraction and quality evaluation by modified Jadad. RESULTS： Totally 19 RCTs were included， involving 1 794 patients. Results of Meta-analysis showed， olanzapine can significantly improve the complete control rate of patients with acute CINV [RR＝1.12，95％CI（1.06，1.18），P＜0.001]， delayed CINV[RR＝1.26，95％CI（1.14， 1.39），P＜0.001]， overall CINV [RR＝1.62，95％CI（1.32， 1.99），P＜0.001] and breakthrough CINV[RR＝2.05，95％CI（1.47， 2.86），P＜0.001]， there were significant differences between 2 groups； there were no significant differences in the incidence of tiredness， dizziness， lethargy and constipation（P＞0.05）. CONCLUSIONS：Olanzapine is safe and effective in the prevention and treatment of CINV and can be recommended in treating breakthrough and refractory CINV. Besides， olanzapine in the prevention and treatment of CINV belongs to “off-label use”， so the clinicians should have a comprehensive consideration of chemotherapy and patients’ consent.