With the development of the economy, technology, and urbanization, the level of physical inactivity increased among people. Especially for the youth, the heavy schoolwork and the lack of awareness of and investment in physical activity opportunities could affect their growth and health literacy for long-lasting healthy and active lifestyles. Access to a safe and enabling environment could bring diverse opportunities for youth to be physically active. To better understand the influence of the physical activity (PA) environment on youth, this dissertation will be associating, understanding, and measuring the relationship between environments and PA with youth health using the GIScience and statistical methods. First, the school surrounding environment and youth health study investigates the spatial correlation between environmental factors and school youth’s fitness outcome based on the elementary school attendance zone. The finding indicates that the inside-school PA environment factor is highly associated with youth health outcomes; also, the park and terrain environment factor indicates strong local geographic variation in youth health. The second study highlights the park-based variables to further understand the outside school and outdoor activity environment for youth, and we use these as our study sites. Using GIS methods and text mining analysis, it uses online review data to quantify how public perception and expectations change in various environments toward youth play in parks. The results show that central public perception and expectation of the youth activity in the park and the disparity distribution of some topics vary in the environmental variables. Lastly, the Physical activity Access Disparity (PAD) index was proposed to measure and map environments and PA for youth. It adopts five dimensions of “access” from healthcare to measure the youth PAD index. These five dimensions are Accessibility, Availability, Accommodation, Affordability, and Acceptability (5 As). The result identifies “play oases” and “play deserts” in the US and Georgia by diverse 5 As combinations. The results from this dissertation bring diverse aspects to analyzing the environment and youth physical activity research using GIScience methods. Future researchers and policymakers could use the framework to fit their preferences and conditions