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Solar radiation (Rs) is a necessary input variable for Penman-Monteith (PM) formula recommended by FAO to calculate reference crop evapotranspiration (ET0-PM). The influence analysis of solar radiation (Rs-c) from Angstrom equation and its parameters on ET0-c calculation based on PM was taken as the objective in nine agricultural regions of China. Using monthly valid average solar radiation (Rs-o) (from dataset of monthly values of radiation data from Chinese Surface Stations) and relative sunshine duration data (from dataset of monthly values of climate data from Chinese Surface Stations) at 112 stations during Jan.1957—Mar.2017, through comparative analysis and correlation analysis, the spatiotemporal differences between Rs-c and Rs-o were mainly explored. Then the spatiotemporal differences between ET0-c and ET0-o were obtained by input Rs-c and Rs-o to PM respectively, and it was also analyzed for illustrating the applicability of Rs-c to ET0-PM calculation in different regions of China. The result showed that Rs-c and Rs-o in the nine agricultural regions had significant and unstable spatial and temporal differences. There may be a large error when Rs-c directly replaced Rs-o to participate in the calculation of ET0-PM. However, the analysis of the spatiotemporal difference of ET0-c and ET0-o showed that whether in the entire continent, or the agricultural regions, ET0-c and ET0-o were characterized by a significant and relatively stable linear correlation, the R2 was more than 067 and the error of mean ET0-c was only 006~026mm/d. Considering Chinas agricultural region types, dealing with the “spring drought” in the northern area of irrigation demand, the application can be directly to get ET0-PM by Rs-c, but for the “summer drought” period nationally, ET0-c was slants bigger than ET0-o, and the corresponding correction model was necessary in the application of high precision of watersaving agriculture. 