Objective To investigate the influence of preservation of the intercostal brachial nerve on sensory function and prognosis after modified radical mastectomy for breast cancer.Methods A total of 84 female breast cancer patients admitted to the Putian Medical District of the 900th Hospital of the Joint Logistics Support Force from October 2019 to October 2020 were selected and divided into the observation group(42 cases)and the control group(42 cases)by random number table method.Both groups were treated with modified radical mastectomy for breast cancer.The intercostal brachial nerve was preserved in the observation group,while the intercostal brachial nerve was not preserved in the control group.The patients were followed up for 1 year.The clinical indicators,sensory function scores,complications and prognosis were compared between the two groups.Results There were no significant difference in operation time,in traoperative blood loss,number of lymph node dissection,the total incidence of complications and the recurrence rate between the two groups(P>0.05).The hospitalization time of the observation group was shorter than that of the control group,and the difference was statistically significant(P<0.05).There was no significant difference in the preoperative sensory dysfunction scores between the two groups(P>0.05).The scores of the postoperative sensory dysfunction in the two groups after surgery were lower than those before surgery,and the scores of the postoperative sensory dysfunction in the observation group after surgery were higher than those in the control group,while the differences were statistically significant(P<0.05).Conclusion Preserving the intercostals brachial nerve in modified radical mastectomy for breast cancer can not prolong the operation time and increase the surgical trauma,and has no significant effect on the surgical effect and prognosis,and is more conducive to the recovery of postoperative sensory function of patients.The clinical application is safe and reliable.