The utility model relates to a steel truss full-welded truss piece. Two ends and middles of two upper chord integral nodes are welded with upper chord rods so that an integral upper chord rod is formed, two ends and middles of two lower chord integral nodes are welded with lower chord rods so that an integral lower chord rod is formed, and diagonal rods, upper ends and lower ends of vertical rods are respectively welded with integral nodes of the integral upper chord rod and the integral lower chord rod. The construction method of the steel truss full-welded truss piece is that two internodes of upper chords are taken as an integral upper chord rod for performing construction, two internodes of lower chords are taken as an integral lower chord rod for performing construction, and the vertical rods, the diagonal rods in the two internodes are welded with integral node plates of the upper and lower chord rods. The steel truss full-welded truss is capable of reducing splicing and welding workload of a construction site, working efficiency is high, construction progress is rapid, and quality is ensured; main truss splicing of one section is reduced, materials are saved; a horizontal construction site welding line of a bridge deck is reduced, splicing work of longitudinal ribs is reduced, work efficiency is high; and the steel truss full-welded truss piece is suitable for simply support steel trusses of roads and railways, continuous steel trusses and steel trusses of steel truss cable-stayed bridges and the like.