Abstract: Dual waveguide rotary joint can convert dual rectangular waveguide to dual coaxial waveguide and then convert dual coaxial waveguide to dual rectangular waveguide. This paper mainly discusses the key techniques and the implementation method of the waveguide rotary joint in a dual band phased array radar. The microwave electromagnetic simulation software HFSS is employed in the design of the Ku-band and C-band rotary joints, which theoretically broadens the bandwith of the joints. The temperature field, the highest temperature and its position in the rotary joint are obtained by thermal simulation, which verifies that the failure of the joint due to high temperature ignition will not occur during operation. A prototype is manufactured and tested. Results show that the electrical performance meets the design requirements.