The invention relates to a VRF (varied refrigerant volume) air conditioning system, which comprises a compressor, an evaporator, a condenser, an outdoor environment temperature sensor and an electronic expansion valve opening degree control device, wherein the electronic expansion valve opening degree control device comprises a controller, temperature sensors, a pressure sensor and an electronic expansion valve, the temperature sensors, the pressure sensor and the electronic expansion valve are respectively in electric signal connection with the controller, the temperature sensors are respectively arranged on an exhaust pipe of each compressor for detecting the exhaust temperature value, the pressure sensor is arranged on a main exhaust pipe of a plurality of compressors for detecting the total exhaust pressure, and the electronic expansion valve is arranged at the back end of the condenser for realizing the throttling on an outdoor unit. The invention also discloses a control method of the VRF air conditioning system. The control method avoids the defects that in the practical use, when the exhaust temperature is too low, excessive coolants are deposited at the air return side of the system, the compression with liquid of the compressor is caused, when the exhaust temperature is too high, the compressor is overheated, and the lubricating oil carbonization of the system is caused. The stable and efficiency operation of the whole system is guaranteed.