The energy of the laser must be converted into other forms of energy in order to have a therapeutic effect on the tissues. 1. Photothermal effect: It refers to the absorption of laser light energy by the tissue and its conversion into heat energy, resulting in an increase in the temperature of the tissue. The laser-induced photothermal effect mainly leads to local hyperthermia, coagulation, hemostasis, vaporization, fusion and selective photothermal effects. 2, light burst effect: generated by pulsed laser, laser energy is converted into acoustic energy, which is mechanical energy, producing a high-impact shock wave, and this impact force may come to burst and crush the tissue. 3, photochemical effect: when the laser energy is absorbed by the tissue and converted into chemical energy, the chemical linkage between the tissue is directly destroyed by laser light energy, while the laser excites these molecules into a biochemically active state. 4.Photodynamic effect: When the photosensitive part of the tissue is under the action of the laser of suitable wavelength, biochemical reaction occurs.