The variation of vegetation coverage is an important indicator of environmental changes. Quantifying impact of human activities on vegetation coverage change has been a hot topic in the field of ecology. Although various vegetation coverage restoration projects have been conducted, relevant researches mainly focused on the project of returning farmland to forest. The role of afforestation project in vegetation restoration is limited at the qualitative acknowledge, without relevant quantitative research reported. In this paper, with Chongqing city as the study area, based on remote sensing, meteorological and statistical data, under the support of GIS technology and residual trend method, the spatiotemporal characteristics of vegetation cover change and the effect of human activities from 2000 to 2020 in mountainous areas of Southwest China were studied from the integrated perspective of normalized difference vegetation index(NDVI) and land-use and land-cover change(LUCC) analysis. The results are as follows:(1) In the recent 20 years, the vegetation coverage in the study area increased overall, and the spatial heterogeneity was strong. The status of vegetation coverage and its restoration tendency in northeast and southeast of Chongqing were superior to center area. (2) Residual analysis showed that human activities had both positive and negative effects on vegetation cover change, while the positive effects were dominant. Areas experiencing the positive impacts of human activity on vegetation coverage restoration were mainly concentrated in the southeast and northeast parts of the study area. In contrast, areas experiencing the negative impacts of human activity were mainly distributed in the center part of the study area. Areas surrounding the urban area of counties could also suffer the negative impacts of human activity. (3) The area of unchanged forestland and the unchanged cultivated land had the greatest influence on the change of vegetation cover (those two land use conversion typesa totaltotally account for 84.18%), and the contribution rate of returning farmland to forest was only 1.24%. (4) There was a significantly positive correlation between the area of afforestation project and the change of vegetation coverage in the area of unchanged forestland (R²=0.82), and the ecological engineering of forest conservancy could explain the residual change of NDVI in the unchanged forest area. The contribution rate list of land-use and land-cover change to vegetation cover change was established in this study, which quantitatively revealed the important role of afforestation project on vegetation cover restoration. The results could provide important reference for the research of vegetation coverage change at regional scale.