As a new generation of hydrodynamic laser system, Er, Cr: YSGG laser has the advantages of accurate cutting, efficient sterilization, anti-inflammatory, and promoting wound healing. Its wavelength is similar to the absorption peaks of water and hydroxyl in hydroxyapatite, which can be absorbed by the oral tissues well. This paper summarizes the operational principle, its application, and research progress of Er, Cr: YSGG laser in orthodontic therapy.