The fact that local anesthesia can not restraint the sense of pain caused by the irradiation of YAG laser light has been discovered in some cases. This phenomenon accounts for the effect of YAG laser in deep organic tissues and the reduced(or lost)efficacy of local anesthesietic results from the irradiation of YAG laser light. In addition, the local anesthesia would also cause the extension of scattering angle(or necrotic area), change the properties and the transmittanne of the laser. All these lead to a conclusion: local anesthesia isn＇t suitable for YAG laser operation.