A cable trench cover plate with a fire extinguishing function relates to the field of power transformation equipment. The cable trench cover plate comprises cover plates which are placed on a cable trench. Guide grooves are formed in the two sides of the cable trench, and a plurality of cover plates are placed in the guide grooves. An inserting mechanism and an inserting slot for connecting adjacent cover plates are arranged on the two sides of each cover plate. A fire extinguishing assembly is arranged at the bottom of the cover plates. The problem that gaps are easily generated between traditional cable trench cover plates and the cover plates cannot be embedded into cable trench cover plate grooves can be solved. The disassembly and assembly are more convenient through the opening-closing design. Through the design of the inserting mechanisms and the inserting slots, the gaps are smaller. Through the design of the fire extinguishing assembly, automatic detection and fire extinguishing can be achieved, and potential safety hazards are eliminated.