Objective: To explore the longitudinal associations between dietary macronutrients and lung function in schoolaged children, so as to provide the nutritional research evidence for promoting children s lung health. Methods: In November 2021, two primary schools located in Chengdu, Sichuan Province were selected from the Southwest China Childhood Nutrition and Growth (SCCNG) cohort by a stratified cluster random sampling method, enrolling a total of 1 112 school aged children aged 8 to 13 years. At baseline, the dietary and sociodemographic characteristics of the children were assessed. One year later, the forced vital capacity (FVC) of the children was measured and converted into Z scores (FVC- Z ), while the vital capacity index (VCI) was also calculated. Generalized linear regression analysis was employed to examine the associations between dietary macronutrients and lung function, considering interactions with gender and age, followed by stratified analysis. Results: After adjusting for confounding factors, the analysis results of the generalized linear regression model showed that the carbohydrate energy ratio was negatively correlated with FVC- Z ( β =-0.02) and VCI ( β =-0.16), while the fat energy ratio showed a positive correlation with FVC- Z ( β =0.03) and VCI ( β =0.23) ( P <0.05). The protein energy ratio was positively correlated with FVC- Z ( β =0.09) and VCI ( β =0.60) specifically in girls ( P <0.05). Additionally, there was an interaction effect of age on the associations between macronutrients and lung function ( P <0.01); in children aged 8-9 and 10-11, the carbohydrate energy supply ratio was negatively correlated with FVC- Z ( β =-0.04, -0.03) and VCI ( β =-0.29, -0.21), and fat energy supply ratio was positively correlated with FVC- Z ( β =0.07, 0.05) and VCI ( β =0.46, 0.32) ( P <0.05). Conclusions There are age and sex differences in the association of dietary macronutrients with lung function, with a low carbohydrate, high fat diet promoting lung function in children. Additionally, protein intake appears to have a positive influence on the lung function of girls. The early school age period may represent a critical window for dietary interventions aimed at promoting lung health.