Objective To study the effect of Er:YAG laser assisted all-ceramic inlay in repairing large area defect of posterior teeth. Methods A total of 54 patients (54 teeth) admitted to the Department of Prosthodontics, Dental Disease Prevention and Treatment Institute of Huangpu District, Shanghai from February 2021 to December 2023 were selected as the research objects. According to the different irradiation time, they were divided into 10 s irradiation group, 15 s irradiation group and 20 s irradiation group, with 18 patients in each group. All patients were treated with Er:YAG laser-assisted all-ceramic inlay restoration. The therapeutic effect, edge pigmentation and restoration after repair, and satisfaction were compared among the three groups. Results There was no significant difference in the degree of tension, pain and overall feeling of the treatment process between the 10 s irradiation group and the 15 s irradiation group, the 15 s irradiation group and the 20 s irradiation group (P >0.05). The proportion of pain grade A in the 10 s irradiation group was higher than that in the 20 s irradiation group, and the proportion of pain grade B was lower than that in the 20 s irradiation group (P <0.05). The proportion of grade A of edge pigmentation in the 10 s irradiation group and the 15 s irradiation group was higher than that in the 20 s irradiation group, and the proportion of grade B was lower than that in the 20 s irradiation group (P<0.05). There was no significant difference in the evaluation of restorations among the three groups (P >0.05). There was no significant difference in repair satisfaction between the three groups (P>0.05). Conclusion Er:YAG laser-assisted all-ceramic inlay restoration has a good effect, which is of positive significance for improving edge pigmentation and pain degree and improving satisfaction. It can improve the repair effect of the prosthesis. In practical application, the irradiation time can be controlled according to the actual situation to maximize its repair effect.