An outdoor unit for a heat recovery VRF air conditioning system, having a first connector and a second connector, and comprising: a compressor, having an exhaust port (a) and a gas return port (b); a reversing assembly, having a first valve port (c), a second valve port (d), a third valve port (e) and a fourth valve port (f), the first valve port (c) being connected to the exhaust port (a), the second valve port (d) being connected to the gas return port (b), and the third valve port (e) being connected to the first connector; an outdoor heat exchanger, having a first end connected to the fourth valve port (f), and a second end connected to the second connector; a plurality of one-way valves, wherein each one-way valve has a circulation end and a stop end, and each one-way valve is opened only in one direction from the circulation end to the stop end; the plurality of one-way valves comprise a first one-way valve, a second one-way valve, a third one-way valve, a fourth one-way valve, a fifth one-way valve and a sixth one-way valve; the circulation end of the first one-way valve is connected to the fourth valve port (f), and the stop end of the first one-way valve is connected to the first end of the outdoor heat exchanger; the circulation end of the second one-way valve is connected to the first connector, and the stop end of the second one-way valve is connected to the third valve port (e); the stop end of the third one-way valve is connected to the first end of the outdoor heat exchanger; the circulation end of the fourth one-way valve is connected to the second end of the outdoor heat exchanger, and the stop end of the fourth one-way valve is connected to the second connector; the circulation end of the fifth one-way valve is connected between the second one-way valve and the third valve port (e), and the stop end of the fifth one-way valve is connected between the fourth one-way valve and the second connector; the circulation end of the sixth one-way valve is connected between the fourth one-way valve and the outdoor heat exchanger, and the stop end of the sixth one-way valve is connected between the first one-way valve and the fourth valve port (f); a throttling element; and a gas-liquid separator, comprising a second inlet (j) and a gas outlet (k), the second inlet (j) being connected to the second valve port (d), and the gas outlet (k) being connected to the gas return port (b), characterized in that, the circulation end of the third one-way valve is only connected between the second one-way valve and the first connector; and the throttling element is connected in series between the third one-way valve and the outdoor heat exchanger. a compressor, having an exhaust port (a) and a gas return port (b); a reversing assembly, having a first valve port (c), a second valve port (d), a third valve port (e) and a fourth valve port (f), the first valve port (c) being connected to the exhaust port (a), the second valve port (d) being connected to the gas return port (b), and the third valve port (e) being connected to the first connector; an outdoor heat exchanger, having a first end connected to the fourth valve port (f), and a second end connected to the second connector; a plurality of one-way valves, wherein each one-way valve has a circulation end and a stop end, and each one-way valve is opened only in one direction from the circulation end to the stop end; the plurality of one-way valves comprise a first one-way valve, a second one-way valve, a third one-way valve, a fourth one-way valve, a fifth one-way valve and a sixth one-way valve; the circulation end of the first one-way valve is connected to the fourth valve port (f), and the stop end of the first one-way valve is connected to the first end of the outdoor heat exchanger; the circulation end of the second one-way valve is connected to the first connector, and the stop end of the second one-way valve is connected to the third valve port (e); the stop end of the third one-way valve is connected to the first end of the outdoor heat exchanger; the circulation end of the fourth one-way valve is connected to the second end of the outdoor heat exchanger, and the stop end of the fourth one-way valve is connected to the second connector; the circulation end of the fifth one-way valve is connected between the second one-way valve and the third valve port (e), and the stop end of the fifth one-way valve is connected between the fourth one-way valve and the second connector; the circulation end of the sixth one-way valve is connected between the fourth one-way valve and the outdoor heat exchanger, and the stop end of the sixth one-way valve is connected between the first one-way valve and the fourth valve port (f); a throttling element; and a gas-liquid separator, comprising a second inlet (j) and a gas outlet (k), the second inlet (j) being connected to the second valve port (d), and the gas outlet (k) being connected to the gas return port (b), characterized in that, the circulation end of the third one-way valve is only connected between the second one-way valve and the first connector; and the throttling element is connected in series between the third one-way valve and the outdoor heat exchanger.