The quantitative estimation of vegetation net primary productivity (NPP) is important for predicting the trend of terrestrial carbon cycle, and the accuracy of the CASA model, which is widely used for NPP estimation, still needs to be improved. Based on the optimization of existing CASA model, we improved the CASA model by considering the dynamic changes of the maximal light use efficiency (LUE_max), compared the simulation results before and after the improvement, and estimated the vegetation NPP in Anhui Province from 2001 to 2020 using the improved CASA model. Results are as follows:(1)the improved CASA model can be applied to the estimation of vegetation NPP in the study area, with significant correlation between simulated NPP and observed date(R²= 0.736, P<0.01).(2)The improved CASA model simulated vegetation NPP in Anhui Province was able to present more details in spatial expression and the temporal NPP values were higher in the growing season and lower in the non-growing season than those in the pre-improvement period, which widened the intra-annual variation of NPP. (3)From 2001 to 2020, the overall NPP of vegetation in Anhui Province showed a fluctuating upward trend, with a multi-year average value of 547.61 gC m^-2 a^-1, and the average annual growth amounted to 2.18 gC m^-2 a^-1, with the fastest growth of NPP was observed between 2016 and 2020. The intra-annual NPP had obviously seasonal differences, which showed that summer>autumn>spring>winter.(4)The vegetation NPP in Anhui Province had strongly spatial differentiation, with a distribution pattern of more in the north and south while less in the middle, with high value areas mainly distributed in the mountainous areas of southern Anhui, the Ta-pieh Mountains area in western Anhui and part of the Huaibei Plain crop areas, and low value areas mostly distributed in the areas with lower vegetation cover density such as Chaohu lake, along the Yangtze River and the Huaihe river basin. During the period of 2001-2020, the vegetation NPP in Anhui Province showed an obviously rising trend, the rising area accounted for 74.04% of the total area, mostly distributed in the flat terrain of the Huaibei Plain.