Abstract: Objective To explore the effect of mindfulness-based music therapy(MBMT) on the cognitive function and emotion in breast cancer patients during chemotherapy and provide support for psychology health practice. Methods The purposive sampling method was used to choose 72 breast cancer patients who had chemotherapy after surgery.They were randomly divided into MBMT group and control group.Both groups received routine nursing care,while the intervention group also received MBMT two times once a week for six weeks.The MMSE scale and POMS scale were used after the intervention to investigate the effect of MBMT on cognitive function and emotion. Results There were no significant difference between the two groups at baseline in all scales(P>0.05).There were two patients run off in MBMT group and one patients run off in the control group.Only 34 patients in the MBMT group and 35 in the control group completed the scales.The t-test showed the directional ability,memory,attention,memory and MMSE total score were improved after the six weeks intervention(P<0.05),the cognitive function and each dimension score in the MBMT group were higher than those in the control group;TMD total scores,anger,tiredness,energy,self-esteem in MBMT group were obviously lower than those in control group,there were significant difference(P<0.05);but not in tension(P=0.247),depression(P=0.066) and confusion(P=0.095) between two group.The score for negative emotion in the MBMT group was lower than that in the control group with a statistical significant(P<0.05). Conclusion MBMT showed a trend toward improving psychological outcomes by enhancing cognitive function and negative emotion in breast cancer patients.