Objective To explore the effect of Hall technique on plaque index and treatment success rate in children with primary molar caries. Methods A total of 80 children with primary molar caries admitted to the Stomatology Center, Suining Central Hospital from March 2024 to March 2025 were selected as the research subjects. According to the random number table method, they were divided into the control group and the experimental group, with 40 children in each group. The control group was treated with traditional resin restoration technique, and the experimental group was treated with Hall technique. The plaque index, treatment compliance, oral treatment comfort, treatment success rate and adverse reaction rate were compared between the two groups. Results The score of plaque index in the experimental group after treatment was lower than that in the control group (P<0.05). The score of FBRS in the experimental group was higher than that in the control group (P<0.05). The score of FPS-R in the experimental group was lower than that in the control group (P<0.05). The treatment success rate of the experimental group (95.00%) was higher than that of the control group (77.50%) (P<0.05). There was no statistically significant difference in the incidence of adverse reactions between the two groups (P>0.05). Conclusion Hall technique can improve the treatment success rate of primary molar caries and effectively optimize the oral environment of children. This technique features high comfort during treatment, good treatment compliance in children and few adverse reactions, presenting excellent overall application effects.