There are several common causes of pain inside the pectoral muscle: a. When female patients are accompanied by malignant tumors of the breast, the tumor cells invade the pectoral muscle as well as the nerves, which will cause painful symptoms in the pectoral muscle. At this time, patients can improve the magnetic resonance imaging and ultrasound examination of the breast to clarify the breast lesions. Surgery should be performed to remove the breast and axillary lymph nodes as soon as possible. After surgery, systemic chemotherapy and local radiotherapy can be combined to reduce the pain of the pectoral muscle and prolong the life of the patient; secondly, the patient may suffer from strain of the pectoral muscle during strenuous exercise or fitness exercise, accompanied by the formation of local hematoma. The location and size of the hematoma can be clarified by ultrasound, and local ice can be applied for 24 hours to reduce bleeding and promote the absorption of the hematoma. 24 hours later, hot amylin packs can be applied externally and oral bruising pills can be taken to reduce the pain of the pectoral muscle.