The invention belongs to the construction field of electric power transformer substation construction projects and particularly relates to an adjustable cable trench construction cover plate for temporarily covering trench faces of cable trenches of different widths. The cover plate comprises an outer cover plate body with the strip-plate-shaped appearance and an inner cover plate body with the strip-plate-shaped appearance. The inner cover plate body is arranged in the outer cover plate body in an embedded or sleeved mode, and the inner cover plate body and the outer cover plate body are in sliding fit relation and move in a set direction. Threaded holes are formed in the inner cover plate body and the outer cover plate body respectively. The multiple threaded holes are sequentially arranged in the moving direction of the inner cover plate body and the outer cover plate body. The inner cover plate body and the outer cover plate body are fixedly connected and matched through bolts. The cover plate is simple in structure, high in practicality and multipurpose, the requirement for covering the cable trenches in the set width range is met, and the application range is wider.