Objective: To explore the effect of replacing rice bowls with trays on controlling the salt intake among school aged children, providing new evidence and insights for salt reduction intervention. Methods: From April to May 2024, 373 students from grades 4-9 at a boarding school in Guizhou Province were enrolled through stratified random cluster sampling, with one intervention class and one control class per grade. During the intervention period for one month, and the types of meals provided, pricing standards, and dining procedures shall remain consistent with daily operations, the intervention group ( n =181) compartmentalized trays for lunch and dinner, while the control group ( n =192) still used a rice bowl. Pre and post intervention assessments included 24 hour urine collection, questionnaire surveys, and physical measurements. The difference in differences analysis combined with multiple linear regression was used to analyze the changes in sodium intake and to evaluate the net effect of the intervention. Results: The post intervention 24 hour sodium intake in the intervention group was ( 2 222.6 ±1 013.6) mg, an increase of 94.6 mg from baseline, with no statistically significant difference ( t=1.10, P >0.05). In contrast, the post intervention 24 hour sodium intake in the control group was (2 080.5±895.7) mg, a decrease of 190.8 mg from baseline, showing a statistically significant difference ( t=-2.39, P <0.05). The difference in differences results indicated that after adjusting the model for factors such as gender, grade and dietary behaviors affecting sodium intake, the intervention group showed a net increase of 232.5 mg [ β(95%CI )=232.5(-40.3-505.2)] in 24 hour sodium intake compared to the control group, with no statistically significant net effect ( P >0.05). Conclusions Merely changing tableware is insufficient to control children s salt intake effectively. Based on continuous practical explorations and evidence based research grounded in the nudge theory, multi dimensional measures such as salt reduction education and the construction of a supportive environment should be integrated to form an intervention system that achieves synergistic and enhanced effects.