In the context of peaking carbon dioxide emissions and achieving carbon neutrality, urban green space, as the main approx-natural ecological space in urban areas, play an essential role in the realization of carbon neutrality through increasing green carbon sequestration and reducing carbon emissions simultaneously. Based on the analysis of approaches and assessment methods of urban green space carbon neutrality efficiency, the paper proposed a comprehensive evaluation framework that combines the efficiency of carbon sink increase and carbon emission reduction of urban green space. Taking the Huangpu District of Shanghai as an example, the article comprehensively evaluates urban green space’s direct and indirect effects on carbon neutrality. It profoundly analyzes the spatial distribution characteristics of the two influencing pathways. The article found through research that the rate, type, and planting of vegetation have a more significant impact on the efficiency of green space for sinking. The rate of green space, the proportion of subsidiary green space, the construction of green nets, the balance of green space distribution, and the construction of waterfront green space have a more significant impact on green space emission reduction efficiency. The article further proposes strategies and methods to improve the overall efficiency of green space carbon neutrality, and aims to measure the value of urban green space in promoting carbon neutrality from a multi-dimensional and systematic perspective and provide a reference for the development and optimization of urban green space.