The grading of squamous cell carcinoma of the skin is a pathological concept, where the tumor is cut down and goes for a pathological examination. During pathological examination, grading will be done according to the amount of atypical cells. It is routinely classified as grade I when the abnormal cells are below 25%; grade II when the abnormal cells account for 25%-50%; grade III when the abnormal cells are 25%-70%; and grade IV when the abnormal cells are >70%. The grading of squamous cell carcinoma is mainly to determine the degree of malignancy during the treatment process and whether further treatment is needed subsequently. The lower the relative abnormal cells, the lower the malignancy will be. If the squamous cell carcinoma is graded at grade I only and does not penetrate the dermis, then the malignancy of squamous cell carcinoma is relatively low, and regular follow-up can be done after removal. However, if the cellular grade of squamous cell carcinoma reaches grade III, even if it is cut cleanly after surgery, adding photodynamic and local radiotherapy may be helpful for prognosis.