The invention relates to a steel-concrete combined type bottom plate bushing box construction process, comprising steps: 1. adopting lateral wall covering bottom board type steel hanging box, laying the bottom board keel above the panel, filling the steel hanging box with concrete; 2. completing splicing of the steel bushing box, welding seam jointing reinforcement on the bottom board, casting down-layer 25cm-thick C40 concrete subsequently; 3. down-lying the steel bushing box in position, synchronously down-lying by a six-group hydraulic jack down-lying device, fine regulating plane positionafter down-lying to the elevation; 4. welding four steel corbels on each steel casing, positioning the top elevation below the bearing platform bottom elevation; 5. installing an overhanging beam, wherein a Phi 32 finish-rolled spiral steel bar is adopted, the steel bracket is connected to a bottom plate hanging point construction, eliminating the down-lying hanging point, completing force systemconversion of the steel hanging box; 6. casting upper layer 75cm thick underwater C30 concrete. The invention is reasonable in construction, capable of reducing steel amount of bottom board; materialsaving, high in strength, light in weight, fast for construction by applying prestressed material in the steel hanging box.