An air conditioner comprising: a compressor having a discharge port and a return port; a reversing assembly comprising a first port, a second port, a third port and a fourth port, wherein the first port is communicated with one of the second port and the third port, and the fourth port is communicated with the other of the second port and the third port, the first port is connected to the discharge port and the fourth port is connected to the return port; an outdoor heat exchanger and an indoor heat exchanger, wherein a first end of the outdoor heat exchanger is connected to the second port and a first end of the indoor heat exchanger is connected to the third port; a heat sink assembly comprising an electrical control element and a heat dissipation subassembly for heat dissipation of the electrical control element, wherein the heat dissipation subassembly is in series connection between a second end of the indoor heat exchanger and a second end of the outdoor heat exchanger; characterized in that, the air conditioner comprises: a one-way throttle valve comprising a first valve port and a second valve port, wherein the first valve port is connected to the second end of the outdoor heat exchanger and the second valve port is connected to the heat dissipation subassembly, in a flowing direction from the first valve port to the second valve port, the one-way throttle valve is fully turned on, and in a flowing direction from the second valve port to the first valve port, the one-way throttle valve is a throttling valve; and a throttling element in series connection between the heat dissipation subassembly and the second end of the indoor heat exchanger; wherein the throttling element provides a throttling effect in a flowing direction from the heat dissipation subassembly to the second end of the indoor heat exchanger, and in a flowing direction from the second end of the indoor heat exchanger to the heat dissipation subassembly. a compressor having a discharge port and a return port; a reversing assembly comprising a first port, a second port, a third port and a fourth port, wherein the first port is communicated with one of the second port and the third port, and the fourth port is communicated with the other of the second port and the third port, the first port is connected to the discharge port and the fourth port is connected to the return port; an outdoor heat exchanger and an indoor heat exchanger, wherein a first end of the outdoor heat exchanger is connected to the second port and a first end of the indoor heat exchanger is connected to the third port; a heat sink assembly comprising an electrical control element and a heat dissipation subassembly for heat dissipation of the electrical control element, wherein the heat dissipation subassembly is in series connection between a second end of the indoor heat exchanger and a second end of the outdoor heat exchanger; characterized in that, the air conditioner comprises: a one-way throttle valve comprising a first valve port and a second valve port, wherein the first valve port is connected to the second end of the outdoor heat exchanger and the second valve port is connected to the heat dissipation subassembly, in a flowing direction from the first valve port to the second valve port, the one-way throttle valve is fully turned on, and in a flowing direction from the second valve port to the first valve port, the one-way throttle valve is a throttling valve; and a throttling element in series connection between the heat dissipation subassembly and the second end of the indoor heat exchanger; a one-way throttle valve comprising a first valve port and a second valve port, wherein the first valve port is connected to the second end of the outdoor heat exchanger and the second valve port is connected to the heat dissipation subassembly, in a flowing direction from the first valve port to the second valve port, the one-way throttle valve is fully turned on, and in a flowing direction from the second valve port to the first valve port, the one-way throttle valve is a throttling valve; and a throttling element in series connection between the heat dissipation subassembly and the second end of the indoor heat exchanger; wherein the throttling element provides a throttling effect in a flowing direction from the heat dissipation subassembly to the second end of the indoor heat exchanger, and in a flowing direction from the second end of the indoor heat exchanger to the heat dissipation subassembly.