To observe the effect of glass fiber post with multiple root canal combined with all-ceramic crown in repairing large area defect of crown. Methods A total of 100 patients with large area defect of crown admitted to the Department of Stomatology, Huayuan Road Community Health Service Center, Haidian District, Beijing from October 2017 to October 2022 were randomly divided into control group and study group, with 50 patients in each group. The control group was repaired with metal post cobalt chromium porcelain crown, and the study group was repaired with glass fiber post with multiple root canal and allceramic crown. The masticatory efficiency, repair effect, repair success rate, gingival crevicular fluid MMP2, ICAM1, ALP levels and complications were compared between the two groups. Results The masticatory efficiency of the study group was higher than that of the control group at 6 months after repair (P <0.05). The proportion of repair integrity, color matching and edge suitability in the study group was higher than that in the control group (P <0.05). The repair success rate of the study group was 96.00%, which was higher than 84.00% of the control group (P <0.05). The levels of MMP2, ICAM1 and ALP in gingival crevicular fluid in the study group were better than those in the control group at 6 months after repair (P <0.05). The incidence of complications in the study group was 4.00%, which was lower than 20.00% in the control group (P <0.05). Conclusion The effect of glass fiber post with multiple root canal combined with all-ceramic crown in repairing large area defect of crown is good, the success rate of repair is high, and the biocompatibility is good. Meanwhile, it can effectively improve the masticatory efficiency of patients. It is a safe and reliable repair method, which is worthy of clinical application.