Disclosed is a direct evaporation type air cooling type fresh air unit. An inlet air valve (13) is arranged at one end of an air conditioning cabinet (1), an air filter (14) is arranged on the inner side of the inlet air valve, a fan (2) is arranged at the other end of the air conditioning cabinet, a first-level refrigerating system, a second-level refrigerating system and a third-level refrigerating system are arranged, the first-level refrigerating system is provided with a first refrigerating circuit, a second refrigerating circuit and a third refrigerating circuit, the first refrigerating circuit, the second refrigerating circuit and the third refrigerating circuit can independently or simultaneously run, a first-level evaporator (11) shared by the first refrigerating circuit, the second refrigerating circuit and the third refrigerating circuit is arranged in the air conditioning cabinet, the second-level refrigerating system is provided with a fourth refrigerating circuit and a fifth refrigerating circuit, the fourth refrigerating circuit and the fifth refrigerating circuit can independently or simultaneously run, a second-level evaporator (6) shared by the fourth refrigerating circuit and the fifth refrigerating circuit is arranged in the air conditioning cabinet, and the third-level refrigerating system is composed of a sixth refrigerating circuit, and a third-level evaporator (4) is arranged in the air conditioning cabinet. The unit can stably run under the wide weather condition, the dehumidification requirement of the air conditioning system is met, the air supply comfort is improved, and moisture condensation is prevented from happening to an air outlet.