NDVI and SPEI drought index are collected and analyzed to investigate vegetation responses to drought regimes at different time scales in different regions and vegetation types across China, and the causes of changes are discussed. The results show that: 1) SPEI and NDVI are significantly positively correlated in most regions of China, indicating that the changes in vegetation biomass are influenced mainly by spatiotemporal characteristics of available water. The southeastern Yangtze River basin and the lower Pearl River basin are characterized by abundant precipitation and vegetation that is not sensitive to drought. The northeastern Heilongjiang Province, the Changbai Mountains, and the western Sichuan Province are characterized by weak correlation between NDVI and SPEI, indicating small effect of drought on vegetation. (2) The effects of the average water balance, average annual rainfall, average annual effective accumulated temperature, and average daily sunshine hours on correlations between NDVI and SPEI show that the average water balance is the key factor behind the changes in vegetation vigor. Hence, it can be concluded that change in soil moisture is the key factor determining the changes in vegetation activity and biomass. Regional precipitation or water balance is related significantly to the correlation between SPEI and NDVI, whereas vegetation in the regions with longer sunshine hours is more sensitive to droughts. In general, grasslands are the most sensitive to droughts, followed shrubs and forest.