Abstract: Urban parklands are the primary creators of natural landscape and ecological environment within cities, and they are the most critical source of ecosystem services (ES) for urban areas. However, the current research on the supply and demand of ES with urban park green space as the research object is not deep enough. Using InVEST and ArcGIS to quantify the ES supply, demand, and supply-demand ratio of parkland in Jinniu District, Chengdu City, for the year 2020, to evaluate its contribution to the district and its ability to meet its own needs as well as those of Jinniu District. The results show that: (1) The ES functions of parklands in Jinniu District, generally perform well, especially in ecological regulation services, but the contribution of food and water provision functions is relatively small; (2) Jinniu District has a large demand for ES, but the demand for various ES in the parklands of Jinniu District is relatively small, with the demand basically increasing from north to south; (3) Except for water provision services, the supply of most ES in the parklands of Jinniu District can basically meet the internal self-sufficiency of the region, but the ES supply of the parklands in Jinniu District can hardly meet the comprehensive demands of Jinniu District. Except for soil retention services, the deficit degree of other ES is relatively large; (4) The imbalance of ES supply and demand in the parklands of Jinniu District, mainly stems from the fragmentation of its spatial distribution and the mixture of various land use types. In the study area, large parklands dominated by forest and green spaces perform excellently in ES functions, on the contrary, parklands with complex land use types and high proportions of construction land perform poorly in ES. The targeted urban green space optimization strategies proposed based on the assessment results are of great significance for the construction of ecological civilization and green space system planning in cities.