Abstract: The Weihe River Basin is an important ecological conservation area in the middle reaches of the Yellow River. It is also a typical region of soil erosion on the Loess Plateau. Monitoring the trend of vegetation growth in the region and analyzing its relationship with climate change and human activities are important for the scientific assessment of regional ecological construction, vegetation and ecological restoration of the Loess Plateau. The normalized difference vegetation index（NDVI）, temperature, precipitation, population density, and land use data from 2000 to 2021 were selected to analyze the spatio-temporal variation characteristics of NDVI in Weihe River Basin, and explore the impacts of climate change and human activities on the trends of NDVI. The results showed that, from 2000 to 2021, NDVI increased in the Weihe River Basin, with an annual average growth rate of 0.004. On the inter-annual scale, NDVI was a positively correlated with annual average precipitation, but not significantly correlated with annual average temperature. On the monthly scale, NDVI had a positive correlation with temperature and precipitation in April and August, and a weak negative correlation with the temperature in July. The change of population density was negatively correlated with the change of NDVI, which indicated that the decrease of population density was beneficial to the restoration and improvement of vegetation. The internal change of land use type was the main reason for the vegetation NDVI change. The decreasing trend of NDVI in the area with significant decrease of NDVI was mainly caused by the decreasing of NDVI of cultivated land in Guanzhong Plain, while the increasing trend of NDVI in the area with significant increase of NDVI mainly resulted from the increase of NDVI in grassland, forest land, and cultivated land in the loess hilly area and loess remnant plateau.

Key words: normalized difference vegetation index （NDVI）, climate, population density, land use, Weihe River Basin