The utility model discloses a cable trench dehumidification device, power protection device technical field, gushes including ventilating, intake stack, bending pipeline the centre that the intake stack arranging the cable pit in and to arrange along cable pit direction level is connected to the lower extreme is gushed in the ventilation, ventilate to gushing the upper end one end that connection elbow said that elevates above the soil, the both ends of intake stack all are equipped with the air intake, bending pipeline's the other end is the air outlet, still including the humidity control mechanism interior with locating the pipeline of noise elimination mechanism who locates bending pipeline air outlet end. During the use, humidity controller is given to the humidity signal transmission of moisture detector in with the cable pit that detects, and when the early warning value who sets for was reachd to humidity when the cable pit in, humidity controller triggered air discharge fan start -up carrying on ventilation and dehumidifies. The utility model discloses simple structure, simple to operate, long service life is equipped with the silencer among the cable trench dehumidification device, reduced the air discharge fan and taken out the noise that produces among the wet process, can not exert an influence to peripheral resident.