Abstract: A method of constructing underpass across railway and highway includes the steps of excavating a traction ditch on one side of the road foundation and a launching ditch on the other; building a traction wall with traction holes therein against the road foundation in the traction ditch; and sequentially tracting a precast box culvert one after another through perforating, anchoring and jack driving according to the construction line until a predetermined configuration is completed thereat. Subsequently, build pier foundations, supports, and a bridging beam; arrange shell pipes; place PC steel reinforcements; and, after a certain curing period, perform prestress operations in the precast box culverts of the structure and grout cement mortar therein. Finally, excavate the earth volume under the structure and finish the road surface of the underpass for opening to traffic.