The utility model discloses an exempt from to destroy fore -and -aft gangway unit mounting structure of main deck paint, it includes the fore -and -aft gangway crossbeam, supporting legs, pipe support, the fore -and -aft gangway pipeline, fore -and -aft gangway cable and fore -and -aft gangway passageway, a plurality of landing legs of fore -and -aft gangway crossbeam bottom installation, the fore-and -aft gangway pipeline has been put to the top and the below equipartition of fore -and -aft gangway crossbeam, the fore -and -aft gangway pipeline installation of below is on pipe support, pipesupport is fixed in at both ends between the adjacent landing leg, fore -and -aft gangway crossbeam overhead has fore -and -aft gangway passageway and fore -and -aft gangway cable, the welding of landing leg bottom has isolating pad board and backing plate, leave certain space between isolating pad board and the backing plate, the backing plate leaves certain space with the main deck. Because destruction is avoided suffering by the paint of upper deck reverse side to save a large amount of touch -up paining work, not only reduced workman's intensity of labour, saved the expense of repairing, the construction cycle of boats and ships has still been shortened greatly.