The invention discloses an anti-condensation ventilation device for a ring main unit, and relates to the technical field of the ventilation devices for the ring main units. The device comprises a supporting seat and a ring main unit body, wherein a first cover plate and a second cover plate are arranged in a ventilation window of an upper plate of the supporting seat; a supporting plate is arranged on one side of the ring main unit body; the ventilation device is arranged above the supporting plate; the ventilation device comprises a motor, a cam, a movable rod, a contact plate and a compression spring; a motor output shaft is connected to the cam; the movable rod is arranged below the cam; the contact plate is arranged between the movable rod and a rotary plate; the contact plate is connected to the upper end of the movable rod; the lower end of the movable rod is hinged to one end, close to the second cover plate, of the first cover plate; and the compression spring is arranged between the contact plate and the supporting plate. According to the anti-condensation ventilation device, hot air in a cable trench can be prevented from entering the ring main unit body to form a condensation phenomenon, a problem that a switch cannot act correctly due to rusting of a circuit breaker and a load switch in the ring main unit body is avoided, the power supply reliability is improved, alarge amount of manpower and material resources do not need to be consumed for erasing condensation of the ring main unit, and potential safety hazards are reduced.