Abstract: With the Tizinafu River Basin of Western China as the study area,the MODIS atmospheric data is used to estimate the spatial distribution of clear-sky atmospheric transmittance based on the Iqbal Model C,and the sky view factor（SVF）and remote sensing surface albedo data are introduced to calculate the topographic obstruction of scattered radiation and the spatial distribution of albedo coefficients of reflected radiation,respectively. Finally,combined with the direct radiation terrain shading effect of the Kumar model to improve the Kumar model. The improved model comprehensively considers the influence of the atmosphere and terrain on solar radiation. The spatial and temporal distribution of surface solar radiation in the study area is simulated and analyzed by the improved model,and the simulation results are verified based on the observation data from ground-based meteorological stations. The results show that the estimated values of the model and the observed values of the sites are in good agreement,with a correlation coefficient R~2 of 0.96,a mean absolute error（MAE）of 1.47 MJ/m~2,and a mean absolute relative error（MARE）of 12.26%. The simulation accuracy of the model is higher in spring,summer and autumn but lower in winter,which may be due to the underestimation of MODIS atmospheric data in winter.