The Inner Mongolia Autonomous Region is an important ecological security barrier in northern China. It is of great significance to study the mechanism of vegetation change and hydrothermal factors in the Inner Mongolia Autonomous Region. Based on normalized difference vegetation index (NDVI) and meteorological data from 1982 to 2020 in Inner Mongolia, a path analysis method was used to analyze the direct and indirect effects of temperature and precipitation on vegetation cover change in Inner Mongolia. The Copula function was used to establish the probability distribution function to describe the dependence of precipitation-NDVI and temperature-NDVI under different values, which provided scientific basis for ecological construction in this region. The result showed that from 1982 to 2020, the precipitation in Inner Mongolia decreased at a rate of 0.357mm/(10a) (P=0.276), the temperature increased at a rate of 0.243℃/(10a) (P<0.001), and the NDVI increased at a rate of 0.009/(10a) (P=0.228), and the improvement area was much larger than the degradation area. Precipitation and temperature inhibited vegetation growth through each other. The comprehensive path coefficient of precipitation on vegetation NDVI was positive (0.927), while the comprehensive path coefficient of temperature on vegetation NDVI was negative (-0.809), and the direct effect of precipitation on vegetation growth was much greater than the indirect effect of temperature. When the precipitation was 7mm (west), 15mm (middle), 20mm (east) and 10mm (whole area) above the threshold, NDVI was greater than 0.16, 0.3, 0.5 and 0.3, respectively, and the vegetation index was increased with the increase of precipitation and joint probability. NDVI was increased with the decrease of temperature from west to east, and the temperature range conducive to vegetation development expanded to the low temperature area, showing a stepped distribution.