The present invention discloses a method and device for dehumidification and condensation prevention of a distribution ring main unit. An adjusting knob (6) is rotated to set a humidity threshold value, the humidity threshold value is transmitted to a humidity control switch device (3), a humidity sensor (2) transmits the detected real-time humidity value to the humidity control switch device (3), the humidity threshold value and the real-time humidity value are displayed through a liquid crystal display (5); the humidity control switch device (3) compares the real-time humidity value with the humidity threshold value, when the real-time humidity value exceeds the humidity threshold value, the output is operated, and a condensation dehydration dehumidifier (4) is driven to operate dehumidification; and when the real-time humidity value is less than the humidity threshold value, the output is stopped, and the condensation dehydration dehumidifier (4) is driven to stop the operation. The method and device for dehumidification and condensation prevention of the distribution ring main unit are simple in structure and high in operability, and thoroughly eliminate the condensation and white dew in the ring main unit to ensure the safety of devices and persons, reduce work time and improve the service life.