Objective: To analyze the association between each regional fat mass and total body bone mineral density (BMD) in children and adolescents aged 7-17 years in Beijing, so as to provide theoretical basis and practical guidance for implementing interventions. Methods: From September to December 2020, a stratified cluster random sampling method was used to select 1 423 children and adolescents aged 7-17 years in Tongzhou District, Beijing. Dual energy X-ray absorptiometry (DXA) was employed to measure regional body composition and total body BMD. Multiple linear regression was used to analyze the association between regional fat mass and total body BMD. Results: The median (interquartile range) fat mass values for total body, upper limbs, abdomen, hips, and thighs were 13.51(8.84, 19.21), 1.59(1.08, 2.23), 0.73(0.39, 1.29), 2.32(1.46, 3.26), 5.29(3.59, 7.21)kg, respectively. After adjusting for covariates, the results of multiple linear regression analysis showed that total body fat mass (β=0.010), abdominal fat mass (β=-0.100), and hip fat mass (β=0.104) were significant associations with total body BMD (all P<0.01). Sexstratified analysis revealed that in boys, total body fat mass (β=0.008) and hip fat mass (β=0.058) were positively associated with BMD, while thigh fat mass (β=-0.038) showed a negative association with total body BMD (all P<0.05). In girls, total body fat mass (β=0.013), hip fat mass (β=0.163), and thigh fat mass (β=0.023) were positively associated with total body BMD, whereas abdominal fat mass (β=-0.196) showed a negative association with total body BMD (all P<0.05). Among children and adolescents with body fat percentage below the standard range, within the standard range and above the standard range, total body fat masses were positively associated with total body BMD (β=0.021, 0.016, 0.015); among children and adolescents with body fat percentage within the standard range while upper limb (β=-0.042), abdominal (β=-0.067), and thigh fat mass (β=-0.018) showed negative associations with total body BMD, and hip fat mass demonstrated a positive association with total body BMD (β=0.082) (all P<0.05). Conclusion Regional fat distribution is associated with total body BMD in children and adolescents, with the nature of these associations varying by sex and body fat percentage.