With the rapid increase of urbanization in recent years, public health has become one of the prominent problems in all countries and developing nations in particular. This article reviews the latest research in children's physical activity in outdoor environments. The existing research on this topic mainly focuses on the following four aspects:1) applying multiple measurement methods including the motion sensor method, action observation, and physical activity questionnaires to investigate the level of children's physical activity; 2) the Study on Children's outdoor spatial system planning and design including research on the spatial differentiation of urban children's outdoor physical activity spatial structure at the city scale and children's playground design at the site scale; 3) the influence of the outdoor environment on children's physical activity including the influence of specific urban planning and land use planning factors and the influence of specific environmental design factors; 4) children's perception of the opportunities for physical activity in the outdoor environment. Finally, this article indicates the further studies that should include influences of specific public open space factors on children's physical activity type and physical activity level; influences of outdoor physical environmental factors on the opportunity of children's physical activity etc.