The structure and energy conservation characteristics of hybrid desiccant cooling system with condensation heat recovery are introduced briefly. Based on the first and second law of thermodynamics, a system thermodynamic model is established and the solution process given in a diagram. The dehumidification capacity is calculated under different exergy efficiency and indoor sensible heat conditions. The calculation results show that the desiccant wheel barely can compensate for the humidity load of outdoor air under with a ventilation rate of providing fresh air once per hour; when the fresh air rate of ventilation is limited to 0.5 times per hour, however, the desiccant wheel possess sufficient capacity under relatively large wheel exergy efficiency and high sensible heat load.