1.Survey: The initial characterization of the swelling is generally based on seven aspects such as the location, size, boundary, mobility, presence of pressure pain, skin temperature and accompanying symptoms. 2.Imaging: B-us, CT, MRI, PET-CT, angiography, etc. MRI is preferred over CT for soft tissue sarcoma of the extremities, and chest CT rather than CR should be performed in high-risk patients (>5 cm, deep location, highly malignant) to exclude pulmonary metastases. 3. Biopsy: Soft tissue sarcoma biopsy, including needle aspiration biopsy and excisional biopsy. The accuracy rate of needle aspiration biopsy is about 85%. If the location of tumor is superficial, it is usually performed by clinicians, and if the location is deep, CT or ultrasound guided needle aspiration can be performed. If needle aspiration is difficult or fails, then surgical excisional biopsy is required. Synovial sarcoma, epithelioid sarcoma and clear cell sarcoma should be examined for regional lymph nodes. In conclusion, the diagnosis of soft tissue sarcoma should be a combination of clinical, imaging and pathology. Only after the diagnosis is clear can further treatment be done.