Scientific understanding of urban ecosystem service value (ESV) is fundamental to building an urban ecological landscape pattern and improving urban environmental quality. The equivalent factor method (EFM) is widely used in evaluating ESV for natural ecosystems. In this study, using the EFM and sensitivity analysis, our research explored the space–time changes in land use and ESV during the planning and construction of Tianfu New Area from 2010 to 2020. This study selected correction factors from natural geography and social economy aspects, and established space–time correction models for standard equivalent coefficients as well as a comprehensive dynamic evaluation model for the ecosystem service value of specific urban areas. In terms of land use, the area of farmland decreased the most. The areas of construction land, grassland, and water bodies increased significantly. The reduced farmland was mainly converted into construction land, followed by grassland and water bodies. Other land use types had smaller changes. Due to the increased area of water bodies and their high-value coefficient per unit area, the urban ecosystem service value showed an increasing trend. During the study period, the conversion of about 1% of land led to about a 0.25% change in the urban ecosystem service value. Farmland in 2010 and water body in 2020 are the most sensitive land factors for ESV in Tianfu New Area. The results might have important insights for urban ecological environment protection and improving ecosystem services during the construction of newly built urban areas.