The invention discloses a locomotive air conditioning controlling system. The locomotive air conditioning controlling system comprises a locomotive air conditioning main control board, a power supply,a condensing fan, a ventilator, a compressor, an electric heater, a fresh air valve, a communication network, a temperature detector, a temperature adjusting switch, a mode controlling switch and a pressure protecting switch connected to the locomotive air conditioning main control board, the power supply is connected with the locomotive air conditioning main control board through a power supplycontrolling port, the condensing fan is connected with the locomotive air conditioning main control board through the input and output controlling ports of the condensing fan, the ventilator is connected with the locomotive air conditioning main control board through the input and output controlling ports of the ventilator, and the compressor is connected with the locomotive air conditioning maincontrol board through the input and output controlling ports of the compressor. The locomotive air conditioning controlling system has the controlling functions such as ventilation, cooling, heating,over-current, temperature detection and fresh air volume adjustment, automatic controlling is achieved through an environment temperature and return air temperature sensor, the manual function is set,and the locomotive air conditioning controlling system can provide the comfortable indoor environment for a locomotive driver cab accordingly.