Abstract: A novel compact power divider, which converts TEM mode of coaxial waveguide to 4-port TE10 mode of rectangular waveguide, is provided to meet the compact requirement of the HPM system. The structure of the compact power divider is given, and a cross rod is adopted in the coaxial transmission line to suppress the high mode reflection. The geometric parameters of the divider are optimized, the S-parameter of -6 dB at the output port and reflection radio below -20 dB of each mode at the input port are obtained. The designed power capability of the power divider is as high as 7.1 GW according to the electric field analysi s, and it is very compact with an axial length only about 0.2 m.