Degraded ecosystems in the karst region of Southwest China have been restored to some extent through a series of ecological conservation projects that started in 2000. However, changes in vegetation during the ongoing rocky desertification control projects occurring in this region since 2008 are not well understood. In this study, we used an enhanced vegetation index (EVI) and gross primary productivity (GPP) derived from remote sensing data to investigate the temporal and spatial patterns of EVI and GPP during 2000-2015. Particularly, we focus on changes since 2008 and the responses of vegetation trends to multiple environmental factors in this region. Results show that the annual EVI increased drastically between 2000 and 2015. In particular, the mean and increasing trend of EVI in 2008-2015 was larger than in 2000-2007 by 6.9% and 85.7%, respectively. Ecosystems with significant increase in EVI accounted for 13.4% of the study area in 2008-2015, where annual GPP also increased remarkably with an average growth rate of 20.58 gC m^-2 a^-1. The contributions of temperature and precipitation to increase in EVI were 28.3%. Land cover changes due to the rocky desertification control projects and increase in atmospheric carbon dioxide and atmospheric nitrogen deposition could be the major factors causing increase in EVI. Furthermore, when we divided the 100 pilot counties in the first stage of the rocky desertification control projects into four groups according to their total area of conservation, the EVI trend attributed to non-climatic factors differed significantly among the four groups. Counties with higher conservation efforts had a larger EVI attributed to non-climatic factors, which indicated that the rocky desertification control projects play an important role in increasing vegetation cover.