In the temperature and humidity independent air conditioning system, the fresh air units, in addition to bear all the new wind load, indoor wet load and part of the indoor cooling load, also need to control the temperature of supply air and prevent condensation. This paper pro-poses a new concept for the construction of fresh air units and found: the heat recovery should be carried out in different ways according to the degree of the exhaust air pollution; the use of water-cooled surface cooler with the combination of direct expansion type can improve the overall energy efficiency of the cooling dehumidification system; the reheat of condensing heat, secondary thermal recovery and the adjustment of supply air temperature can achieve through the use of double condenser and double expansion valve structure.