Air conditioning system and control method and device for air conditioning system

The invention relates to the technical field of refrigeration equipment, and discloses an air conditioning system which comprises a first compressor, a second compressor, a third compressor and a fourth compressor. An air suction port of the second compressor is connected with the second liquid separator; the first pipeline comprises a condenser, a second throttling valve, a first electromagnetic valve and an evaporator which are connected in series, and a first pipeline port corresponding to the condenser is connected with the first exhaust port; two ends of the first bypass pipeline are respectively connected with the first exhaust port and the air suction port of the second liquid separator, and the first bypass pipeline is provided with a fourth electromagnetic valve; two ends of the second pipeline are respectively connected with the evaporator and an air suction port of the second liquid separator, and the second pipeline is provided with a fifth electromagnetic valve; two ends of the second bypass pipe