Abstract: A refrigeration system provided with a rotary compressor, a refrigeration pipe line system connected with the compressor and having a gas-liquid separator for separating an injection pressure gas refrigerant, and a gas injection channel extending from a gas zone of the separator and having an open-close valve. The compressor is provided at its cylinder block with an injection pressure port opening to a pumping chamber and with a valve chamber communicating with the port. A by-pass passage channel communicating with the suction port side of the chamber extends from the valve chamber, and a control valve having a communication aperture and a spring, are housed within the valve chamber, the injection channel is connected with a back chamber of the control valve within the valve chamber, so that the open-close valve may be operated to control a capacity of the refrigeration system.