Objective To compare the application value and aesthetic effect of glass ionomer cement and light-curing composite resin in the filling of proximal caries in posterior teeth. Methods A total of 82 patients with proximal caries in posterior teeth who visited the Department of Stomatology of our hospital from August 2022 to March 2025 were selected, and they were divided into the control group and the observation group by the random number table method, with 41 patients in each group. The control group was filled with light-curing composite resin, and the observation group was filled with glass ionomer cement. The filling success rate, periodontal health indicators, secondary caries rate and aesthetic indicators were compared between the two groups. Results The filling success rate of the observation group (93.33%) was higher than that of the control group (76.67%) (P <0.05). The scores of PLI, GI, BI and PD in the observation group after treatment were better than those in the control group (P <0.05). The incidence of secondary caries in the observation group (3.33%) was lower than that in the control group (13.33%) (P <0.05). The proportions of grade A in color matching degree, edge integrity and surface gloss of the observation group were lower than those of the control group (P <0.05). Conclusion The application of glass ionomer cement in the filling of proximal caries in posterior teeth can reduce the risk of secondary caries, maintain periodontal health, and has a higher clinical success rate; while light-curing composite resin performs better in aesthetic effect.