Surface hydrothermal plays a key role in vegetation pattern by affecting soil-atmosphere water exchange and vegetation growth water use. MODIS Leaf area index (LAI) from 2000 to 2020 was used as the evaluation index of vegetation greenness in Qinling-Daba Mountains. Land surface temperature (LST) and temperature vegetation drought index (TVDI) in the same period were obtained based on remote sensing technology to indicate surface hydrothermal conditions. Combined with terrain factors such as aspect and altitude, the temporal and spatial characteristics of vegetation greenness in Qinling-Daba Mountains were analyzed by mean and trend methods. The correlation between vegetation greenness and surface hydrothermal, as well as the leading factors affecting the change of vegetation greenness were explored by time-delay correlation analysis and dominant factor analysis. The nonlinear relationship between vegetation greenness and surface hydrothermal was discussed with the help of the generalized additive model and vegetation types. The results showed that:(1) the LAI of Qinling-Daba Mountains was concentrated in the range of 1-5. The average value of LAI increased first and then decreased with altitude, while the LAI varied greatly in different aspects, which was shown as the north slope of Daba Mountains > the south slope of Daba Mountains > the south slope of Qinling Mountains > the north slope of Qinling Mountains > the west Qinling Mountains. The LAI high value area in the Qinling-Daba Mountains was consistent with the area with good surface hydrothermal in terms of spatial distribution. The LAI low value area was consistent with LST low value area or TVDI high value area. (2) The LAI of the Qinling-Daba Mountains mainly changed from increase to decrease, and the change trend of altitude differentiation was larger than aspect differentiation. In the area of LAI from increase to decrease, surface hydrothermal was mainly from increase to decrease, followed by continuous increase. (3) The LAI of Qinling-Daba mountains was significantly positive correlation with LST, but significantly negative correlation with TVDI. The time lag effect of surface hydrothermal on LAI was not obvious, and LAI was more affected by TVDI than LST. (4) Except for the increase of LST which led to monotonous increase in LAI of deciduous broad-leaved forest and mixed forest, the surface hydrothermal had nonlinear effects on the LAI of various vegetation types. There was a certain threshold, and the response law of LAI on both sides of the threshold was different, and the thresholds of different vegetation's response to surface hydrothermal were quite different.