The invention provides a dehumidification device and system, and relates to the technical field of electric power equipment. The dehumidification device is characterized in that a first humidity sensor is used for acquiring the humidity inside electric power equipment to obtain a first humidity; a second humidity sensor is used for acquiring the humidity outside the electric power equipment to obtain a second humidity; a calculation unit is used for calculating the difference between the first humidity and the second humidity to obtain a first difference value; when the first humidity is lessthan or equal to the second humidity and the first humidity is greater than a preset humidity, a control unit controls ventilation equipment to be a turn-off state and controls a dehumidifier to be ofa turn-on state; when the first humidity is greater than the second humidity and the difference value is less than or equal to a first preset difference value, the control unit controls the ventilation equipment to be of a turn-off state and controls the dehumidifier to be of a turn-on state. The dehumidification device solves a technical problem that the existing dehumidification device cannot take dehumidification measures which are more suitable for actual conditions in the field in a targeted manner because the existing dehumidification device cannot take corresponding effective measureswhile saving the energy.