Photodynamic therapy (PDT) is a minimally invasive therapeutic modality that can selectively treat malignant and benign diseases by using a combination of photosensitizers, light, and oxygen molecules. The light source is one of the three key elements of PDT, and its emission wavelength, irradiation method, and dose directly determine the efficiency of PDT. According to the required performances of light sources for clinical treatment, the technical advantages of light-emitting diode (LED) as light source in PDT applications are discussed. The LED array light source, and the development of wearable and implantable novel PDT light sources based on the organic LED, quantum dot LED, and wireless powered LED are introduced in depth. The application status of LED in isolated cells, live animals, and clinical PDT is summarized comprehensively. The development of LEDs with tunable emission wavelengths and the real-time adjustment of the illumination area and dose are the future development trends of intelligent and personalized PDT light sources.