Abstract: Taking Chongqing, a typical hilly and mountainous city, as an example, the improved water conservation capacity assessment model was constructed based on the Net Primary Productivity(NPP), and the spatial distribution of water conservation function and importance level of ecosystem was analyzed. The results show that in 2019, the annual average NPP in Chongqing was 934 gC·m⁻², the annual precipitation was between 500~1400 mm, and the improved annual average Water Retention Index (WRI) was 0.04. The overall spatial distribution pattern of the water conservation capacity in Chongqing is high in the northeast and southeast and low in the west. The WRI shows a clear mountain context, and areas with high water conservation capacity are distributed along the mountain ridges. The extremely important grades of water conservation function are distributed in the northeast and the southeast of Chongqing, where there are a large number of continuous forests, while the extremely important grades are distributed in a narrow and long belt in the west of Chongqing, mainly concentrated in the vicinity of mountain ranges. The important grades are interspersed between the extremely important grades, mainly in districts and counties such as Fengjie, Yunyang, Zhongxian, Qijiang. The general important grades are interspersed among important grades, mainly concentrated in the west of Chongqing. In the extremely important grade area, forest and grassland account for 33.8% and 54.8%, respectively. The improved WRI combines the advantages of remote sensing technology and couples the information of vegetation and precipitation, it can monitor the water conservation capacity in hilly and mountainous areas in a quantitative, spatial and fine-grained manner.