The invention discloses a novel overlapping structure for a rear coaming and a side coaming. The overlapping structure comprises a rear floor, a rear wheel bulge, a rear coaming lower cover plate, a rear coaming side plate, a rear coaming connecting plate, a rear coaming supporting plate, a rear stand column inner plate, a rear side coaming inner plate and a rear side coaming outer plate, wherein the lower end of the rear wheel bulge is overlapped with the rear floor; the rear coaming lower cover plate is overlapped with the rear floor; the rear coaming side plate is overlapped to the rear floor; the lower end of the rear coaming connecting plate is overlapped with the upper end of the rear coaming lower cover plate, and the lower end of the rear coaming supporting plate is overlapped with the upper end of the rear coaming side plate; the lower end of the rear stand column inner plate is overlapped to the upper end of the rear coaming connecting plate and the upper end of the rear coaming supporting plate; a cavity structure is formed by the surrounding of the rear side coaming inner plate, the rear wheel bulge, the rear coaming side plate and the rear coaming supporting plate; and the lower end of the rear side coaming outer plate is overlapped to the rear floor and coated on the rear side coaming inner plate. According to the novel overlapping structure disclosed by the invention, the light weight design requirements of automobiles are achieved; besides, the developing cost of a mould of the rear side coaming inner plate is reduced, the material utilization rate is improved, and the developing cost of the whole automobile is reduced; and the novel overlapping structure disclosed by the invention has high strength and high torsional rigidity.