Abstract: By MS-800 model precision spectral pyranometer and MS-11 Shadow Band Stand,the solar diffuse radiation D (band of 300-2800nm ) and its components of the spectral diffuse radiation Du (300-390nm ),Db(390-470nm),Dg (470-530nm),Do (530-630nm ),Dr(630-700nm ),Dn( 700-2800nm)were measured during 1989-1990 in Beijing,China.Based on the data observed.the diffuse radiation energy distribution in various spectral bands and its change feature,as well as the effects of the solar declination,solar elevation and cloud etc.on it were discussed.