A dehumidification•evaporation cooling-based all-fresh-air air conditioning system according to one embodiment of the present invention may provide, a dehumidification•evaporation cooling-based all-fresh-air air conditioning system changes a humidity, temperature and enthalpy of an external air which is provided from an external air inlet, to provide a changed first air to an air conditioning space or discharge a second air stayed in the air conditioning space from the air conditioning space to an outlet, the dehumidification•evaporation-based all-fresh-air air conditioning system comprising, a piping module configured to provide a transfer passage of the external air, the first air and the second air, a humidity control unit configured to controls the humidity of the external air, wherein the humidity control unit located on the piping module, a temperature control unit configured to control temperature, humidity and enthalpy of supplied air to be the first air, wherein the temperature control unit located on the piping module, a path setting unit configured to change a transfer path of the external air, the first air and the second air, wherein the path setting unit located on the piping module and a control unit which decides the transfer path of the air from the external air inlet to the air conditioning space or the air conditioning space to the outlet, and controls the path setting unit for transferring air to the decided transfer path based on a first information related to a humidity, a temperature and an enthalpy of the external air.