Normally the wet air condenses easily on the aircraft’s cabin cold surface. The condensed water brings extra weight and corrode the air-frame structure. So a desiccation system is established to deal with the air at the top of the passenger cabin. This paper establishes the physical model and mathematical control equations of the silica-gel desiccant wheel. Jurinak model was used to calculate the outlet parameters, and the system performance was evaluated based on 3 indexes and exergy efficiency. The results show that the changing trend of dehumidification capacity, dehumidification effectiveness, exergy efficiency，dehumidification COP are different; all indexes should be weighed in system design and the performance is obviously improved by adding heat recovery structure.