Abstract: The principles for designing waveguide directional coupler and waveguidepower-divider are systematically presented in the paper. A brief and practicalmethod for designing these components are described in detail. At once thebandwidth parameter is choosen, the relative coupling factor is determined. If thetotal coupling factor is given, then the diameters of the coupling holes, the mostimportant ones in the designing parameters are calculated by means of the calcu-lator 58 C through 58 C-84 A programm.