Microwave two-dimensional transmission waveguide used in high-power millimeter wave directional coupler

The invention discloses a microwave two-dimensional transmission waveguide used in a high-power millimeter wave directional coupler, which comprises a first auxiliary waveguide block, a second auxiliary waveguide block and a sealing flange, the second auxiliary waveguide block is used for upwards introducing microwaves coupled by the directional coupler and transmitting the microwaves to the second auxiliary waveguide block; the sealing flange is used for vacuum sealing and fixing the first auxiliary waveguide block and the second auxiliary waveguide block to form a microwave channel together with the first auxiliary waveguide block and the second auxiliary waveguide block; and the second auxiliary waveguide block is connected to the output port of the first auxiliary waveguide block, protrudes out of the rectangular groove in the back surface of the directional coupler, and is used for changing the position of the rectangular waveguide microwave output port in the first auxiliary waveguide block so as to ens