To analyze the effect of prefabricated fiber posts in oral prosthetic treatment and their impact on periodontal index. Methods A total of 80 patients who underwent oral prosthetic treatment in our hospital from January 2022 to June 2023 were randomly divided into observation group and control group, with 40 patients in each group. The control group was treated with plastic fiber post repair, and the observation group was treated with prefabricated fiber post repair. The repair time, repair success rate, bite force, masticatory efficiency, periodontal index and complication rate were compared between the two groups. Results The repair time of the observation group was shorter than that of the control group, and the success rate of repair was higher than that of the control group (P <0.05). After treatment, the bite force and masticatory efficiency of the two groups were higher than those before treatment, and those in the observation group were higher than those in the control group (P <0.05). After treatment, the scores of PLI, PD and BI in the two groups were lower than those before treatment, and those in the observation group were lower than those in the control group (P <0.05). The incidence of complications in the observation group was 2.50%, which was lower than 15.00% in the control group (P <0.05). Conclusion The application of prefabricated fiber post in oral prosthetic treatment is effective, which can shorten the repair time, improve the success rate of repair, and effectively improve the bite force, masticatory efficiency and periodontal index, with higher application value.