Er, Cr: YSGG laser is called erbium laser. It can be strongly absorbed not only by water molecules, but also strongly absorbed by organic matter and inorganic hydroxyapatite in solid biomass. It can use less energy to get a greater effect, This advantage is beyond the reach of other wavelengths of laser, so it not only can cut soft tissue accurately, but also can cut enamel dentin efficiently without causing thermal damage to dental pulp.The working principle of the laser is that transferring the energy to the coaxial water-air mixture by using the fluid dynamics, and powerful absorption of laser energy by atomized water particles with producing the expansion and acceleration. High-energy and high-kinetic energy water beams formed by high velocity arrangement, and then cutting soft tissue fastly.