Abstract: The rapid development of cities may cause the supply of park green spaces to deviate from the planning goals, resulting in increasingly severe contradiction between the supply and demand of park green spaces. In order to explore the disparity between supply and demand of park green spaces and deal with the limitations of supply-demand research scale, this research, with grid of 500 m×500 m as the basic research unit and the requirements for classification and setting of park green spaces as the threshold, adopts the Gaussian two-step floating catchment area (Ga2SFCA) method and the supply-demand measurement method to analyze the changes in the spatio-temporal distribution of the accessibility and spatio-temporal disparity between the supply and demand of park green spaces in the main urban area of Harbin in 2010 and 2018 respectively. The result shows that the supply level of park green spaces in the main urban area of Harbin fails to meet the requirements of urban green space planning standards. Although the area of park green spaces increases, the unreasonable spatial allocation exacerbates the imbalance between supply and demand of park green spaces. It is speculated that such factors as construction period, land resources, urban planning and market mechanisms mainly affect the supply-demand disparity of park green spaces. According to the matching results of supply and demand, the research proposes a targeted optimization strategy for the layout of park green spaces, in hope of providing a fine and effective reference for improving the balance between supply and demand of park green spaces.