The invention discloses a cable trough cover plate prefabricated template and a construction method thereof. The cable trough cover plate prefabricated template comprises a cuboid template box body and cover plate reinforcing steel bars; the interior of the template box body is hollow; the template box body is provided with a bottom surface and four walls, and is free of an upper cover; the upper edges of the four walls of the template box body stretch outwards to form an edge; the bottom surface, the four faces and the edge of the template box body are integrally cast to form one body; the cover plate reinforcing steel bars are formed by vertically welding a plurality of horizontal reinforcing steel bars arranged in parallel and a plurality of vertical reinforcing steel bars arranged in parallel. The cable trough cover plate prefabricated template disclosed by the invention is firm in structure, convenient to operation, free of assembling and high in construction efficiency, dense vibration of concrete can be guaranteed in the construction process, the pouring quality of concrete is guaranteed, cover plate dimensions and finished product protection are guaranteed, and the edge of a cover plate is not broken.