To meet the demand of high power microwave measurement, a broadband waveguide directional coupler of X-band is presented. In order to achieve the requirements of broadband, a multi-hole coupling structure is adopted，which uses the Chebyshev function to get each coupling coefficient, and gets the initial diameter of each hole by hole-coupling theory. A broadband coupler meeting the design requirements is obtained through optimization with simulation software. According to the simulation results, the coupling coefficient of the system is 40 dB within 8.2–12.4 GHz, the in-band fluctuation is less than 1 dB, and the isolation is more than 30 dB, the measured coupling coefficient is 38–39 dB, the reflection is less than -20 dB, the power capacity is 0.84 MW, which is suitable for MW level high power microwave pulse measurement.