In order to obtain higher output power, the design and research of four-channel high-power microwave combiner with the method of polarization orthogonal mode coupling is proposed in this paper. The TE11-mode has vertical and horizontal polarizations with very different coupling coefficients. The electromagnetic wave coupling and energy transmission are designed and verified with same polarization direction in the two-way three channel coupler. Finally, a feasible four-way high-power microwave combiner is designed to make four-way microwave combined and output based on their theory and simulation. The combiner is mainly composed of input section, coupling section and output section. The four input ports are connected to four input section. The output section is connected to output port. The four microwaves use the long and narrow coupling slots coupled to the main-channel, and output through the common port. By electromagnetic simulation software, the energy coupling efficiency of the sub-channel to main-channel can reach more than 95%, which can efficiently realize the high-power efficiency combination of four-way microwave, and provide an application path for power combiner. Directional couplers are widely used in many fields which are related to microwave. The development of technology is putting higher requirements for directional couplers with broadband and higher power capacity. Waveguide structure, with its large power and simple processing process has become the basis structure of high power directional couplers. An synthesis method for X band power based on circular waveguide. In this paper, a four-road synthesis of circular waveguide coupler is proposed, the cylindrical waveguide which is joined with the output port is named main channel, and the other cylindrical waveguides are called associate channel, the four associate channel are respectively back to back with the main channel. The energy of associate channel which uses long slits is coupled to the output port of main channel, and the coupling energy efficiency of the associate channel is above 95%.