The invention mainly discloses a multifunctional cover plate for a cable duct. The technical scheme is as follows: the multifunctional cover plate for a cable duct includes a cover plate and a fan body, four corners of the cover plate are provided with cut-through air inlets, a cut-through mounting hole is arranged in the middle of the cover plate, the fan body includes an unpowered fan and a positioning seat, the positioning seat is connected with the unpowered fan, a side part of the positioning sea is symmetrically provided with a pair of sliding blocks and a pair of positioning holes, positioning devices are arranged in the cover plate and located at two sides of the mounting holes, the positioning devices are movably connected with the positioning holes, a lower side of the cover plate is provided with a temperature and humidity detection device and a rotary device, and the rotary device rotates the temperature and humidity detection device to a lower side of the mounting hole. The multifunctional cover plate for a cable duct has a ventilation function, achieves a heat dissipation and cooling effect, reading and checking of data are performed through the temperature and humidity detection device, and humid air inside the cable duct is prevented from entering a ground control cabinet and electrical cabinet and causing insulation reduction or potential safety hazards to internal electronic and electrical elements.