Abstract: on the principle of rotor dehumidification is proposed. A dynamic simulation model was constructed based on the TRNSYS platform. The heat and mass transfer process of the rotor was simulated through the dehumidification rotor module，and the anti-condensation effect was simulated and studied according to the local climate to determine the dehumidification capacity of the rotor that meets the anti-condensation requirements of the ring main unit，providing a theoretical basis for the design of the device. Subsequently， an anti-condensation device based on the principle of rotor dehumidification was designed and developed. Through the design of double-layer air ducts，the layout of four air outlets in the same direction and the vertical split structure，the adaptation problem of compact space and high energy consumption in the ring main unit was solved. Practical application shows that the device can effectively eliminate condensation during the rainy season and in low-temperature and high-humidity environments, ensuring the safe operation of the equipment. This verifies the feasibility and efficiency of the small rotor dehumidification technology in preventing condensation in ring main units.