Objective To explore the effect of double taper fiber post restoration on masticatory efficiency and periodontal indexes in elderly patients with premolar residual crowns. Methods A total of 40 elderly patients with premolar residual crowns admitted to our hospital from September 2023 to September 2024 were selected as the research subjects. According to the random number table method, they were divided into the control group and the observation group, with 20 patients in each group. The control group received parallel fiber post restoration treatment, and the observation group received double taper fiber post restoration treatment. The masticatory efficiency, periodontal indexes, quality of life, treatment satisfaction and complications were compared between the two groups. Results After treatment, the masticatory efficiency in the two groups was higher than that before treatment (P <0.05), but there was no significant difference in the masticatory efficiency between the two groups after treatment (P >0.05). After treatment, the PLI in the two groups was lower than that before treatment, and the PLI in the observation group was lower than that in the control group (P <0.05). After treatment, the GI in the two groups was lower than that before treatment (P <0.05), but there was no significant difference in the GI between the two groups after treatment (P >0.05). After treatment, the scores of all dimensions of the quality of life in 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). The treatment satisfaction rate in the observation group was 100.00%, which was higher than 60.00% in the control group (P <0.05). The incidence of complications in the observation group was 10.00%, which was lower than 50.00% in the control group (P <0.05). Conclusion The application of double taper fiber post restoration and parallel glass fiber post restoration in elderly patients with premolar residual crowns can both improve their masticatory efficiency and periodontal indexes. However, the former has more advantages in improving patients' plaque index and quality of life, and the incidence of complications after restoration is low, which is beneficial to further improving the treatment satisfaction.