The invention provides a semi-trailer dumper frame structure. One end of the semi-trailer dumper frame structure is of a framework structure, and the other end of the semi-trailer dumper frame structure is of a cross coupling structure. The framework structure comprises upper wing panels, lower wing panels, middle webs, an outer web, a dumper frame cross beam and a sliding plate, wherein the upper wing panels and the lower wing panels are arranged in parallel; each middle web is fixed in the middle positions of the corresponding upper wing panel and the corresponding lower wing panel to form an I-shaped beam; the two I-shaped beams are fixed to two sides of the dumper cross beam respectively; the bottoms of the I-shaped beams and the dumper frame cross beam are fixed together and slide together. The semi-trailer dumper frame structure largely improves the torsion resistance of a dumper frame after a compartment is lifted. When a compartment bottom plate longitudinal beam and a subframe are in an overlapped state, a cross coupling is additionally welded to a dumper frame rotary shaft, the strength of the dumper frame can be improved, the rollover resistance is good, and the stability of a whole dumper is high.