The study aims at clarifying the performance of desiccant rotor, and at obtaining the design aspects of high efficient desiccant rotor and systems. In the paper, theoretical analysis is performed for rotary dehumidifier and humidifier. The validity of the model is confirmed by comparison between experimental data and calculation. The influences of several complex factors such as adsorption/desorption time ratio, air flow path patterns and air conditions on rotor performance are examined. It is clarified that there is an optimum angle of adsorption, desorption and purge zone becoming a maximum amount of humidifying And also, there is an optimum desorption side air flow rate. It is confirmed that air flow rate and air temperature influence significantly the amount of dehumidifing and humidifing. Furthermore, it is suggested that heat transfer enhancement of the rotor is efficient in the mass transfer enhancement at the beginning of desorption process.