With the development of population aging, the incidence of malignant tumor is increasing year by year. According to the data collected by the National Cancer Registration Center in 2017, the incidence of malignant tumor in China is about 278.07/100 Thousand. With the development of cell biology, the treatment of tumor by inducing apoptosis has been recognized and studied in experiment and clinic. Photodynamic therapy means that sensitizer and oxygen molecules can participate in photodynamic effect. Damage or even necrosis of tumor cells, Because of its ability to regulate metabolism, simple operation and easy to obtain, Low-level laser has been gradually applied to the basic research and clinical practice of tumor, and has become another method of tumor treatment after surgical treatment, chemotherapy and radiotherapy. In this review, the theoretical basis and clinical verification of LLLT for different pathways of tumor apoptosis were reviewed. It is summarized as follows.