Abstract: Two　practical 　downward　continuation　methods　are 　proposed 　for 　the 　sea 　surveying　areas 　inaccordance　with　their 　gravit y　characteristics 　and　available 　information 　addressing　the　uncertainty　of downward　continuation 　for 　airborne 　gravit y　data．In　the 　first 　methodthe 　continuation　corrections 　are calculated　by　using　the　upward　continuation　of 　satellite 　gravit y　data and 　in 　the　other by　using EGM2008gravit y　field　model．A　satellite 　gravit y　data　settwo　sea－borne　gravit y　data 　setsand　an　airborne　gravit y　data 　set 　are 　used　as 　a　case 　stud y　to 　test 　the 　efficienc y　of 　these　new　methods．