Objective:To explore the effects of online mindfulness-based stress reduction(MBSR)on the anxiety and depression status,and quality of life in the caregivers of patients with severe mental disorders.Methods:Ninety-three caregivers for patients with schizophrenia or bipolar disorder,who were hospitalized in Yunnan Provincial Mental Hospital in March 2021,were enrolled and randomly divided into control group(n=47)and MBSR intervention group(n=46).Both groups received basic health education and rehabilitation skill training,while the intervention group received additional online MBSR for 8 weeks.The anxiety and depression status,and the quality of life of the caregivers were evaluated by Self-rating Anxiety Scale(SAS),Self-rating Depression Scale(SDS)and the 36-item Short Form Health Survey(SF-36)before and 8 weeks after intervention,respectively.Results:Thirteen caregivers dropped out of the study,and 80 subjects(40 in each group)were included in the final analysis.At the baseline,there were no significant differences in SAS,SDS and SF-36 scores between two groups(all P>0.05).Compared with the baseline,SAS and SDS scores in the intervention group significantly decreased after 8 weeks of intervention(both P<0.01)and were significantly lower than those in the control group(both P<0.01).There were no significant changes in the control group(all P>0.05).Except the physiological function dimension,the total score and the scores of each dimension of SF-36 in the intervention group were significantly increased after 8-week intervention(all P<0.05),and were significantly higher than those in the control group(all P<0.01).There were no significant changes in the control group before and after intervention(all P>0.05).Conclusion:Online MBSR can reduce the anxiety and depression levels,improve the quality of life in the caregivers of patients with severe mental disorders.