Objective : To evaluate the clinical effects of resin infiltration in treating molar-incisor hypomineralization. Methods : Twelve patients (36 teeth) with mild molar-incisor mineralization imperfecta who met the inclusion criteria were selected and treated with penetrating resin. Before treatment (T0), at the one-week follow-up (T1) and at the six-month follow-up (T2), a Crystaleye spectrophotometer was used to take photos, and the color differences (ΔE) between the lesion area and the surrounding normal enamel area at different times were calculated and analyzed. The area of the lesion and the total area of the labial surface of affected teeth were calculated using Adobe Photoshop CS3 software. The corresponding area ratio (R) and treatment efficiency (SR) were obtained. The R value was used to judge the effectiveness of resin penetration in the treatment of molar and incisor mineralization imperfecta and to evaluate its aesthetic effect. The results were analyzed by repeated measures one-way ANOVA. Results: The color difference of the lesion area vs sound adjacent enamel (ΔE) decreased significantly, and that of the lesion area decreased significantly after resin infiltration (P < 0.001). The success rate was approximately 86.02%, which means that the esthetic effect of resin infiltration in treating molar-incisor hypomineralization was remarkable. No important adverse events or side effects were observed. Conclusion The aesthetic effect of resin infiltration in the treatment of mild molar and incisor hypomineralization is good. This method is recommended for clinical use.