The invention discloses a circular waveguide elbow. The circular waveguide elbow comprises a waveguide elbow body, the waveguide elbow body comprises a first structural member and a second structuralmember locked with the first structural member to form a waveguide channel, the outer wall of the first structural member is fixedly provided with a first liquid cooling heat sink for liquid cooling and heat dissipation, the outer wall of the second structural member is fixedly provided with a second liquid cooling heat sink for liquid cooling and heat dissipation, the first liquid cooling heat sink and the second liquid cooling heat sink are symmetrical around the contact surface of the first structural member and the second structural member, the two ends of the first and second liquid cooling heat sinks are all fixedly provided with liquid cooling joints used for connecting with a liquid inlet pipe or a liquid outlet pipe, any one of the first and second liquid cooling heat sinks is theliquid inlet pipe, the other one is the liquid outlet pipe, the cooling liquid flows in from a liquid inlet tank, flows through the whole feed source waveguide and then flows out from a liquid outlettank. The liquid inlet pipe, the liquid outlet pipe and the liquid cooling joints are connected with the cooling liquid, the liquid cooling joints are located at the two ends and located along with the liquid cooling heat sinks with no need for extra addition of a circular waveguide elbow to increase space use.