Abstract: The laser pulse transmitted by satellite laser altimeter bends for atmospheric refraction and extends the ray paths, and it is necessary to correct the atmospheric delay to get accurate ranging results. The hydrostatic delay is the major component of total zenith delay, which is only decided by surface pressure. The hydrostatic equation of static atmosphere was deduced under the condition of non-ideal gas, and surface pressure model was established relevant to geopotential height. Combined with the meteorological data of NCEP and position and elevation data of GLAS, the surface pressure was calculated by numerical integration of 4 order Runge-Kutta algorithm, and then the hydrostatic delay was obtained. Through the respective comparisons between the hydrostatic delays got by this method and the NCEP estimated surface pressure with the GLAS official results, the trend and accuracy of this method are both better with the maximum error less than 2 cm. It is concluded that the hydrostatic delay of satellite laser altimeter can be corrected effectively and accurately by the method based on hydrostatic equation and numerical integration.