Active commuting to school plays a crucial role in promoting physical activity and positively contributes to children's physical and mental health. While extensive attention has been paid to the impact of built environment on children's active commuting to school, there is still a lack of consideration for the joint effects and differences in the impact of built environment of neighborhood and school. In this study, a crossclassified multilevel model is employed to investigate the effects of neighborhood and school built environment on children's active commuting to school in Xi'an. Our findings indicate that: ① Neighborhood built environment has a greater impact on children's active commuting to school compared to school built environment; ② Neighborhood and school built environment factors that affect children's active commuting to school are different. For instance, while an increase in the number of school bus stops promotes active commuting to school, factors such as mixed land use, number of school cafeterias, and number of intersections contribute negatively to children's active commuting. ③ Built environment moderates the effect of distance to school on active commuting to school. An increase in the number of neighborhood stores exacerbated the negative effect of distance on active commuting to school; neighborhood population density, number of bus stops, and school greenery promoted active commuting to school by weakening the negative effect of distance. These research outcomes hold significant implications for developing public policies and spatial adjustments that aim to promote active commuting to schools among children.