Objective To explore the difference between the application of onlay and all-ceramic crown in premolar restoration. Methods A total of 100 patients who underwent premolar restoration in our hospital from August 2021 to August 2022 were randomly divided into reference group and inquiry group, with 50 patients in each group. The reference group was repaired with allceramic crowns, and the exploration group was repaired with onlays. The aesthetic repair effect, long-term efficacy, periodontal status, chewing function, complications and repair satisfaction were compared between the two groups. Results The excellent and good rate of aesthetic repair in the exploration group was 98.00%, which was higher than 82.00% in the reference group (P <0.05). The long-term total effective rate of the study group was 98.00%, which was higher than 86.00% of the reference group (P <0.05). The probing depth, gingival index and plaque index in the exploration group were lower than those in the reference group (P<0.05). The bite force and masticatory efficiency of the study group were higher than those of the reference group (P <0.05). The incidence of complications in the study group was lower than that in the reference group, and the repair satisfaction was higher than that in the reference group (P <0.05). Conclusion The effect of onlay treatment in premolar restoration is better than that of all-ceramic crown treatment, and the aesthetic effect and long-term effect are better. Meanwhile, it can promote the rapid recovery of periodontal status and masticatoryfunction, reduce the risk of complications, and improve patient satisfaction. It is worthy of clinical application.