Vegetation ecosystems are crucial for vegetation carbon sinks and represent an important path towards achieving China's carbon neutrality goal. In this study, global daily NEP (Net Ecosystem Productivity, NEP) simulation data products from 1981 to 2019 were selected to analyze the spatial and temporal evolution of vegetation carbon sources/sinks in China. The impacts of climate change and human activities on vegetation carbon sources/sinks were determined, and the effectiveness of ecological restoration and control projects on vegetation carbon sinks was quantified. The BFAST model was used to monitor the annual range of NEP inter-annual changes and to identify 2001 as the time breakpoint. The temporal and spatial characteristics and driving factors of NEP changes between 1981 and 2001 and between 2001 and 2019 were analyzed and compared. From 1981 to 2001, vegetation carbon sinks showed a widespread decreasing trend, with an NEP average of 17.59gC/m². However, from 2001 to 2019, the growth trend of vegetation carbon sinks in northern China changed significantly, with a NEP average of 35.64gC/m². The changes in vegetation carbon sources/sinks in northern China between 1981 and 2001 were mainly due to the influence of climatic factors, which led to a weakening of vegetation carbon fixation capacity. The North China and Northwest regions were mainly affected by precipitation, while the Northeast region was mainly affected by radiation changes. From 2001 to 2019, most of the changes in the NEP were influenced by precipitation and radiation. However, in the Sichuan and Chongqing regions, the impact of temperature and radiation on vegetation carbon fixation capacity was more significant. Human activities caused a change of 4% in vegetation carbon sources/sinks between 1981 and 2001, mainly distributed in the Northeast and Southwest regions. From 2001 to 2019, the proportion of vegetation carbon sources/sinks affected by human activities increased to 26.23%, of which the proportion of enhanced vegetation carbon fixation capacity accounted for 25.22%. The negative impact of climate change on vegetation carbon fixation capacity decreased by about 30% compared to that from 1981 to 2001, indicating that human activities reduced the negative impact of climate change on vegetation ecosystems to a certain extent. The net carbon storage value in 2019 showed significant growth compared to that in 2001, and the economic efficiency of ecological restoration and control investment was positively correlated with most ecological regions. In addition, vegetation carbon sinks in northern China were effectively improved. Therefore, in order to address climate change and protect the ecological environment, it is necessary to actively promote ecological restoration and control investment to achieve sustainable development of the economy, society, and environment.