The invention discloses a stair evaporative airplane ground air conditioning unit. The stair evaporative airplane ground air conditioning unit comprises an air supply system, a refrigerating system and a bypass adjusting system; the air supply system comprises a filter, a first evaporator, a first water stopping plate, a second evaporator, a second water stopping plate, an air supply machine, a flow equalization board and a third evaporator; the a refrigerating system comprises a compressor, an oil separator, a condensate fan, an air cooling condenser, a mixing working medium separator, a plate-type evaporative condenser, a liquid storage device, a gas-liquid separator, an evaporating pressure controller, a thermostatic expansion valve and an electromagnetic valve; the bypass adjusting system comprises a bypass electric adjusting valve and a return air temperature sensor; and the first evaporator, the second evaporator and the third evaporator of the air supply system are connected with the refrigerating system through a refrigerating pipe. The stair evaporative airplane ground air conditioning unit solves the problem of low efficiency in traditional design, the system is simple, the refrigeration performance is high, the system reliability is high, and the application scope is wide.