•The NANI peaked in 2020, representing a 54.41% increase compared to 1990.•The proportion of food/feed nitrogen input to NANI was the highest, reaching 62.30%.•The spatial pattern of NANI exhibited a decreasing trend from east to west and from north to south.•The spatiotemporal changes of NANI are related to the intensity of human activities.•Population density and GDP were the most influential socioeconomic factors impacting NANI. The issue of global nitrogen overload is widely acknowledged as a pressing concern, with excessive nitrogen input resulting from human activities posing a significant threat to regional security. Notably, China emerges as a prominent contributor, exhibiting one of the highest anthropogenic nitrogen inputs worldwide. This study employs the Net Anthropogenic Nitrogen Input (NANI) as a pivotal tool to scrutinize the spatial and temporal patterns of nitrogen input in China spanning from 1990 to 2020. The total NANI reached its zenith in 2020 at 723,378.80 kg·km−2·yr−1, marking a noteworthy 54.41 % increase from 1990. Among the various nitrogen sources, food/feed nitrogen input prevails, constituting 62.30 % of NANI, followed by atmospheric nitrogen deposition at 30.05 %. In less developed regions, primary contributors to NANI include nitrogen fertilizer application and crop nitrogen fixation. The spatial distribution of NANI exhibits a diminishing trend from east to west and north to south. Conducting a quantitative analysis, this study elucidates the impact of socioeconomic factors on NANI in China. Population density (r = 0.97) and GDP (r = 0.91) emerge as primary influencers, with agricultural factors such as livestock breeding (r = 0.70), grain production (r = 0.40), and fertilizer application (r = 0.65) following suit. In addressing the environmental challenges posed by excessive nitrogen, future mitigation strategies should prioritize enhancements in manure management practices and the implementation of pollution reduction facilities.