Downward solar irradiance at the surface of the Earth is derived from the apparent satellite reflectance measurements from GMS 5 visible channel （0 4-1 1μm） based on a physical model of earth atmosphere system. The absorption and scattering of atmospheric molecule and aerosol on clear day are considered with standard mid latitude summer atmospheric model using the 6S

the scattering for other weather is abtained from the real time satellite albedo and the surface albedo acquired from the satellite measurements under clear sky condition. The effects of variations of aerosol and precipitable water on clear day to the surface solar irradiance are considered. Compared to the real time measurements by surface pyranometer

the correlation coefficient is as high as 95%

the deviation is about 10% of mean daily solar insolation. From the comparison

the accuracy of hourly solar irradiance estimated from GMS 5 in the text is improved.