The invention discloses a direct-evaporation type fresh-air processing system using high-temperature domestic wastewater as a cold (heat) source, wherein a water suction pipe of a first-level water pump is provided with a filter, and a water sucking mouth of the first-level water pump is arranged at the bottom of a heat preservation header tank; a drain pipe of the first-level water pump passes through a heat exchanger and then is connected into the heat preservation header tank; the mouth of a water suction pipe of a second-level water pump is arranged at the bottom of the heat preservation header tank, and a drain pipe of the second-level water pump passes through an outdoor heat exchanger of a direct-evaporation type fresh-air processing machine set in a heat exchange mode; and another pipeline of the heat exchanger is connected with a domestic water pipeline. The fresh-air processing machine set uses the high-temperature domestic wastewater as the cold (heat) source to replace the prior air source so that the working condition of the machine set is greatly improved and the efficiency is improved. By using the heat energy of the high-temperature domestic wastewater to preheat the domestic water supply, the heating energy consumption of water supply can be reduced. The system has the advantages of simple and practical structure and obvious energy saving effect.