Abstract: Urban parklands are the main builder of urban natural landscape and ecological environment, which are the most critical source of ecosystem services (ES) for the city. However, the current research on the supply and demand of ES with urban parklands as the research object is not deep enough. Using InVEST and ArcGIS to quantify the ES supply, demand, and supply-demand ratio of parklands in Jinniu District, Chengdu City in 2020, and to evaluate the contribution of its supply to Jinniu District and its ability to meet its own needs as well as those of Jinniu District. The results showed that: (1) The ES function of parklands in Jinniu District was generally good, especially in ecological regulation services, but the contribution of food and water supply function was relatively small; (2) The demand for ES in Jinniu District was relatively large, but the demand for various ES in the parklands of Jinniu District was relatively small, and the demand basically showed a trend of increasing from north to south; (3) Except for water supply services, most of the ES supply in the parklands of Jinniu District could basically meet the internal self-sufficiency within the region, but the ES supply of the parklands in Jinniu District could hardly meet the comprehensive demands of Jinniu District. Except for soil conservation services, the deficit degree of other ES was relatively large; (4) The imbalance of ES supply and demand in the parklands of Jinniu District was mainly due to 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 performed well in ES functions. On the contrary, parklands with complex land use types and high proportions of construction land performed poorly in ES functions. Based on the assessment results, the targeted urban green space optimization strategy is of great significance for the construction of ecological civilization and green space system planning in cities.