Based on the analysis of more than 30-year radiation data from radiation observation stations,the distribution of correlation between solar radiation and sunshine are analyzed.Then this paper mainly discusses the geographical distribution and seasonal variations of a,b coefficients in the climatic formula of solar total radiation.It is necessary to consider the seasonal variation of the a,b coefficients when calculating the solar radiation.The possible error of the climatic calculation of solar radiation is analyzed and discussed.The error range of calculating solar radiation using sunshine data is acceptable.