Erbium, chromium: yttrium scandium gallium garnet (Er, Cr: YSGG) laser is mainly used for root canal treatment, periodontal disease, tooth decay, dentin hypersensitivity, pulp amputation, etc in the field of dentistry. This paper mainly describes the research progress of Er, Cr: YSGG laser in root canal therapy from following four aspects: root canal sealing, sterilization, cavitation effect and the effect on periapical tissue. The experimental results showed that when the operation parameters of Er, Cr: YSGG were 2 ~ 4 w and 20 Hz, it could effectively remove the stained layer of dentin tubules and improve the tightness between materials and dentin. The thermal effect produced by Er, Cr: YSGG energy has a sterilizing effect, while the optical conductivity of the tooth enables the rinse solution to enter deeper tissues, further improving the sterilizing effect. Er, Cr: YSGG also has a cavitation effect, which destroys the surface tension of the deep solution, removing the stain layer and bacteria in the deep layer. However, with the same operation parameters, if Er, Cr: YSGG is not used properly, the thermal effect of Er, Cr: YSGG will cause some damage to the periapical tissues. Therefore, reasonable use time of Er, Cr: YSGG and water cooling conditions are important.