Objective To compare the effect of resin direct filling and inlay repair in patients with posterior dental defect. Methods A total of 80 patients with posterior dental defect admitted to the Department of Stomatology, Eastern District of Suzhou Municipal Hospital from December 2020 to December 2022 were randomly divided into control group and observation group, with 40 patients in each group. The control group was given direct resin filling, and the observation group was given inlay repair. The masticatory efficiency, gingival health status, marginal fitness of restoration and complications were compared between the two groups. Results After treatment, the masticatory efficiency of the observation group was higher than that of the control group (P <0.05). After treatment, plaque index, gingival bleeding index and periodontal pocket depth in the observation group were lower than those in the control group (P <0.05). The proportion of grade A repair edge tightness in the observation group was higher than that in the control group (P <0.05), but there was no significant difference in the proportion of grade B and grade C of the repair edge between the two groups (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 effect of inlay repair in patients with posterior dental defect is better than that of resin direct filling, which can improve the masticatory efficiency and gingival health status of patients. Meanwhile, it is conducive to improving the marginal fit of repair, and the incidence of complications after repair is lower, the safety is higher