Urban parks are vital ecological recreational places, and their spatial evolution has a certain influence on the ecological environment and quality of citizens’ daily life. Taking Beijing as an example, this paper firstly explores the dynamic evolution of urban parks in Beijing by comparing spatial distribution characteristics in three time points of 2005, 2010, and 2017. Besides changes in number and area, the spatial structure and accessibility are examined by the methods of directional distribution, kernel density estimation and network analysis. Then three-factor analysis method is used to explain the evolution mechanism. The results reveal that there exist obvious and continuous growths in urban parks regardless of quantity, area or accessibility. According to the core-periphery spatial distribution pattern, Beijing has gradually formed a systematic green recreational network, and the service area of urban parks by walking within 30 min is 58.6 % of total area. Stability factors, dynamic factors and random factors play important roles during the spatial evolution of urban parks through restraint mechanism, supply-demand mechanism and triggering mechanism respectively. The findings offer both theoretical construct and policy recommendations for the development and sustainability of urban parks in Beijing and other rapidly urbanizing cities with high population densities.