Abstract: Disclosed is a multi-split air conditioner capable of refrigerating and heating simultaneously. A heating circuit consists of a compressor (1), an oil-gas separator (2), a four-way valve (3), indoor heat exchanging systems (12,16,21,22), an outdoor heat exchanger (7), a four-way valve (3), and a gas-liquid separator (26) connected in series along the refrigerant flow direction. A refrigerating circuit consist of a compressor (1), an oil-gas separator (2), a four-way valve (3), an outdoor heat exchanger (7), indoor heat exchanging systems (12,16,21,22), and a gas-liquid separator (26) connected in series along the refrigerant flow direction. A parallel pipeline is arranged at a pipeline between the outdoor heat exchanger (7) and the indoor heat exchanging systems (12,16,21,22), and is utilized for connecting an second electronic expansion valve (8) with a second one-way valve (9) in parallel. A series pipeline is arranged with a third control valve (5) and a third one-way valve (6).