The application discloses a main bridge steel structure construction method and relates to the technical field of bridge construction. The specific steps comprise the following steps: dividing regions, installing baffle plates and
pier columns, installing steel
pipe piles and platform support columns, installing inter-column supports and sliding beams to form sliding tracks, repeatedly constructing the south
bank, completing platform support covering a river, installing lower chord rods and lower bridge decks, installing upper chord rods and upper bridge decks, installing upper-layer cantilevers and lower-layer cantilevers, assembling sliding units, repeatedly assembling sliding units until closure, hoisting the last sliding unit and completing installation of the main bridge steel structure. The construction method can reduce operation risks, shorten construction period, save materials and reduce costs.