There is the information content of atmospheric water vapour in direct solar radiation measured with a solar spectrometer. A deduction approach is presented for retrieving the columnar water vapour content. On the basis of the random model rather

than the Bouguer Law

the retrieval for water vapour absorption is more reasonable. Three Water vapour absorbing bands

α

β

ρ στ

are selected in the joint deduction of water vapour content。 It is shown that the columnar water .vapour content from the remote sensing data is quite consistent with that from radiosonde data.