Objective  To explore the methods of protection of the nerves and blood vessels of pectoralis major muscle in type Ⅱ modified radical mastectomy,and analyze its significance.Methods  The clinical data of 21 patients with type Ⅱ modified radical mastectomy in recent 4 years were retrospectively analyzed.The motor nerves of pectoralis major muscle and blood supply vessels were precisely separated and preserved before pectoralis minor muscle was resected during operation,and pectoralis major muscle was also reserved.The lymphadenectomy were performed according to Halsted radical mastectomy.Results  All the operations in 21 patients were performed smoothly,and the nerves and blood vessels of pectoralis major muscle were reserved after pectoralis minor muscle was resected.The wounds healed well,and the function recovered satisfactorily of ipsilateral upper extremity and shoulder joint satisfied.Conclusion  The precise protection of the nerves and blood vessels of pectoralis major muscle in type Ⅱ modified radical mastectomy ensures improving the postoperative function of ipsilateral upper extremity and shoulder joint and postoperative living quality.