The invention discloses an overpass bridge design construction method applicable to incremental launching method construction and belongs to the technical field of variable cross-section girder body design construction. Main construction operation can be away from a spanned space, it is guaranteed that an existing railway, highway or city road is not interfered by construction, and underbridge safety is ensured, and the overpass bridge design construction method is an alternative scheme when rotation construction is not suitable. The design construction method comprises the steps that temporary tubular pile foundation treatment is conducted, and sliding plate foundations, sliding layers and incremental launching back girders jointed with bridge pier foundations enable a jointed foundation composed of foundation connection girders, bridge bearing table foundations and bridge girders to drive a variable cross-section girder body to conduct simultaneous incremental launching to further achieve being folded with an overline on the other side. The method is suitable for an overpass bridge which spans the railway, the highway or the city road and located in a narrow site with dense city buildings and without rotation construction conditions.