Abstract: Based on the data of direct radiation measured at 9.30, 12.30 and 15.30 true solar time daily at 65 solar radiation stations in China, up to 1978,the atmospheric transparency coefficient has been calculated. For the convenience of comparison among various regions and for presenting distribution charts, the data have been corrected to M=2. Solar constant is taken as S0=1.98 cal/cm2 min.Topography affects atmospheric transparency significantly, high transparenc being on the plateaus while low value in lowlands. The distribution characteristics of the two major factors affecting the atmospheric transparency, water vapour and aerosol, are analyzed. The radiation absorbed by water vapour is calculated according to Muegge and Mueller formulae using the vapour content in air column obtained from radiosonde data.