Principle: ALA photodynamic therapy (ALA-PDT) is to apply photosensitizer precursor 5-aminoketovaleric acid (ALA) topically on the lesion, and ALA is selectively absorbed by the lesion tissue and converted into photosensitizer-protoporphyrin IX (PpIX). The activated photosensitizer releases a large amount of free radicals and singlet oxygen, which destroys the cellular structure of the diseased tissue and can lead to the shrinkage of the diseased blood vessels or tumor tissue to achieve the treatment purpose. The most important feature of this method is that the treatment process has little or no damage to normal tissues. Photodynamic therapy is a new technology of tumor treatment that started to take shape in the late 1970s, which has been officially approved by the relevant departments of the national government abroad and has been recognized and widely used internationally. Since malignant tumors have the characteristics of infiltrative rapid growth, easy metastasis and recurrence. It is difficult to rely on any kind of treatment alone to eradicate tumors and take into account the survival quality of patients. Photodynamic therapy plays an important role in the comprehensive treatment of tumors due to its unique advantages and good compatibility.