The invention discloses an improved pressure-bearing compound drain pipe and a preparation method thereof. The drain pipe comprises a pipe body, wherein spiral reinforcing ribs are arranged on the surface of the pipe body; the pipe body comprises an inner layer and an outer layer; a gap exists between the inner layer and the outer layer; connecting ribs connecting the inner layer and the outer layer are arranged in the gap; the connecting ribs are uniformly arranged along the circumferential direction of the gap and are spirally arranged along the length direction of the pipe body; a plastic layer different from the pipe body in color is arranged on the inner wall of the pipe body; the pore diameters of the left and right ends of the pipe body are consistent; adjacent pipe bodies are in direct butt joint connection by hot melting; cavities are formed in reinforcing ribs; and corrugated pipes are arranged in the cavities. The improved pressure-bearing compound drain pipe is good in ring-stiffness and deformation resistance. The plastic layer is smooth and level, sewage can pass through favorably, and the improved pressure-bearing compound drain pipe is unlikely to scale. Moreover, adhesive joints on the pipe body are covered, so that the improved pressure-bearing compound drain pipe is unlikely to leak and good in sealing property; and the adjacent pipe bodies are in direct buttjoint connection by hot melting, so that the process is simple, and the work efficiency is improved greatly.