Climate change and large-scale ecological restoration have led to significant changes of vegetation in the drylands of northern China, and quantifying the relative contributions of climate change and anthropogenic activities to vegetation dynamics is essential to ecosystem management and coping with future climate change in dryland ecology. The temporal dynamics (before and after the implementation of large-scale ecological restoration projects in 2000) and spatial heterogeneity (along the aridity gradient) of the impact factors of vegetation change in the drylands of northern China still need further quantitative studies. Based on multi-source data, our study analyzed the spatial and temporal patterns of climate and vegetation changes in the drylands of northern China from 1981 to 2018 by using trend analysis, partial correlation analysis and random forest model. We then quantified the relative contributions of climate change and human activities to vegetation dynamics before and after 2000 and their spatial heterogeneity along the aridity gradient. The results indicated that:(1) the average leaf area index (LAI) increase rate in the drylands of northern China was (0.0037±0.0443) a^-1 during 1981-2018, and increased along the aridity gradient. Temporally, only 10.46% of the area was experienced a significant vegetation greening trend before 2000, while 36.84% (P<0.05) after 2000 in the drylands, and vegetation greening was mainly attributed to non-tree vegetation. (2) The positive effect of precipitation on vegetation greening increased in all aridity gradients after 2000, while temperature shifted from positive promotion to negative inhibition in semi-arid and dry sub-humid areas, and radiation shifted from negative to positive effect in arid areas. (3) Climate change dominated vegetation dynamics both before 2000 and after 2000, with contributions of 96.07% and 73.72%, respectively. The contribution of human activities further increased after 2000 (from 3.93% to 26.28%) and strengthened along the aridity gradient, the most significant increase of human-induced LAI trend was found in the semi-arid area (+0.02887 m² m^-2 a^-1, P<0.05). These results can provide scientific references for the restoration and sustainable development of the drylands of northern China in response to future climate change.