Abstract: Objective To explore the effect of olanzapine in cancerrelated depression and anxiety and the adverse reaction.Methods One hundred and seventy-nine patients with cancer-related depression and anxiety from April 2013 to July 2013 were randomly assigned into control group（n=89） and observation group（n=90）. The control group was given psychological support therapy including encouragement， help， compassion and empathy. While only the observation group received olanzapine： 5mg／day oral during radiotherapy or chemotherapy for two weeks. The treatment completion status and toxic side effects of olanzapine during use were recorded. The Zung self-rating depression scale（SDS） and selfrating anxiety scale（SAS） were employed to evaluate the status of depression and anxiety before treatment， at 2nd， 4th and 6th cycle during chemotherapy or after radiotherapy.Results The completion rates of chemotherapy at 4th and 6th cycle were higher in observation group versus control group（P＞0.05）. The SAS scores at 2nd， 4th and 6th cycle and SDS scores at 4th and 6th cycle during chemotherapy of observation group were lower than those of control group（P＜0.05）. The toxicity of olanzapine includes sleepiness， weight gain， dizziness， fatigue， dry mouth， constipation and peripheral edema. Conclusion Olanzapine can improve cancer-related anxiety and depression with the well-tolerated adverse effects.