In this study, we selected Hunan province as the study area. The vegetation NPP and its changes from 2000 to 2013 were calculated using improved Carnegie-Ames-Stanford Approach (CASA) model with MODIS-NDVI data at a 250 m×250 m spatial resolution and meteorological data. Furthermore, we quantitatively analyzed the correlation between NPP and climate for various land-cover types so as to provide reliable information for local environment and sustainable development. The results indicate that: (1) The annual amount of NPP decreased from 41.62 Tg C/yr in 2000 to 125.40 Tg/yr in 2013, with an average being about 86.34 Tg C/yr. In general, the total amount of NPP has decreased obviously since 2000, with an annual rate of about 2.70 Tg C/yr. (2) The annual NPP from 2000 to 2013 had significant spatial differences throughout the study area, decreasing from the southwest to the northeast. There were obvious differences over various vegetation divisions. (3) According to the changes rate of NPP from 2000 to 2013, the study area could be divided into five regions, namely, extremely remarkable increase rate (slope > 0, p < 0.01), remarkable increase rate (slope > 0, 0.01 ≤ p < 0.05), unnoticeable rate (p ≥ 0.05), extremely remarkable decrease rate (slope < 0, p < 0.01) and remarkable decrease rate (slope < 0, 0.01 ≤ p < 0.05), which accounted for 5.40%, 2.02%, 61.64%, 16.79% and 14.15%, respectively. In general, NPP decreased from 2000 to 2013 over different land-cover types, among which, the most significant change took place in grassland and forestland, followed by other types of land, construction land and farmland. (4) The spatial distribution of NPP had higher correlation with precipitation than with temperature.