The invention provides a makeshift road roadbed and a construction method thereof. The method comprises arranging a fence structure on a road surface, wherein the fence structure is a ring with both openings, paving reinforced support frames on the road surface within the fence structure, erecting a freezing tube above the reinforced support frames, filling the fence structure with a solid-liquid mixed filler, starting a freezing device pre-connected to the freezing tube and freezing the solid-liquid mixed filler. The construction method is free of pavement digging, does not damage aboveground vegetation and does not need the freezing device when the makeshift road is not used. The solid-liquid mixed filler can be automatically unfrozen. The fence structure, the reinforced support frames and the freezing tube can be recovered and produce small influence on the environment. The makeshift road roadbed is prepared from the solid-liquid mixed filler through freezing and has a high bearing capacity, high erosion resistance and a low construction cost.