Studying the spatial interactions between socio-economic and natural (SEN) factors and physical health (PF) can help improve national physical and mental health and develop health policies. In order to deeply analyze the relationship between social and economic environment, sports activities, and national physical and mental health, and improve the level of national physical and mental health, this study used mathematical numerical analysis methods using MATLAB and ArcGIS software to determine the determining factors of PF differences in China. The reported National Fitness Composite Index (NFCI) in China was extracted from the National Physical and Mental Health Fitness Monitoring Bulletin in 2015. The SEN factors were gathered from the China Statistical Yearbook in 2015. The OLS model and GWR model were then utilized to investigate the SEN factors of the NFCI. We found that the NFCI of each province had a strong relationship with the natural environment. The NFCI of the eastern coastal regions was higher but also similar to that of the central and western regions. It was also found that the impact of the natural environment on national physical and mental health fitness was greater than that of social and economic factors. Temperature and hours of sunshine were major environmental factors. Annual hours of sunshine (ANNsun, hours), health care expenditure (HEAexpe, Chinese yuan), annual temperature (ANNtem, °C), road distance (ROAdis, kilometers) and annual rainfall (ANNrai, millimeters)are socioeconomic and natural (SEN) determinants of factors and physical fitness (PF). We should increase physical exercise, change our concepts of health, develop a healthy lifestyle and improve our physical fitness in accordance with the national fitness strategy. The regression coefficients obtained by the GWR model show significant differences, indicating that the degree of influence of social, economic, and natural factors on national physical fitness varies significantly with geographical regions..