In order to realize the directed radiating of Ku-band HPM (high-power microwave), a RL-CTSA (radial line continuous transverse stub antenna) was proposed. The antenna was fed by circularly polarized coaxial TE₁₁ mode and radiated by a concentric CTS (continuous transverse stub) array after the wave propagation through a double-layered radial line waveguide. The interspace between adjacent stubs along radial direction was equal to one guide wavelength, a shorting pin was located at the end of the upper radial line waveguide and the space between the pin′s surface and the innermost CTS radiator′s center was half a guide wavelength. As a result, the HPM-RL-CTSA works on standing wave. An antenna prototype with a height of 80 mm and an aperture radius of 285 mm operating at 14.25 GHz has been designed, which has a gain of 35.3 dBi, reaching an aperture efficiency of 47%. The reflectance of this antenna is less than -25 dB and the radiation efficiency is more than 99.0%. The simulated results indicate that this antenna has a power handing capacity of more than 1 GW.