The utility model provides a dampproofing ventilation cover plate of cable pit, relates to the automatic dampproofing ventilation technology of a cable pit, removes the problem that damp automation degree is low in order to solve the inside cable ditch. Bottom apron for the rectangle, be provided with the recess in a set of relative edge of bottom apron, be equipped with vent and apron notch on the bottom apron, driving motor fixes on the bottom surface of bottom apron, and driving motor's drive gear is located apron notch department, the pull apron is through the recess and bottom apron sliding connection of bottom apron, be provided with the gear troughed belt on the bottom surface of pull apron, the gear troughed belt is through the drive gear transport connection of apron notch with driving motor, a stop piece and no. Two stop pieces are all fixed on the bottom apron, and a stop piece and no. Two stop pieces are located the both sides that the pull was lapped respectively. Beneficial effect has good using value and extensive market spreading value for the dampproofing degree of automation who ventilates is high. Be applicable to the inside cable ditch.