Abstract: In an airborne laser barthymetry,various environmental background noises influence the performance of the system.After systematic analysis of environmental background noises,it is obtained that the main noise is the solar noise;comparily,moon noise power and starlight noise power are much lesser.Variation of receiving noise power is chiefly determined by its surface irradiance,not by the airborne height.It also gives the max mensurable depth of the sea in condition of various background noises.