Abstract: An X-band high power microwave leaky-wave-antenna array with one-dimension scanning capability is introduced in this paper. The antenna contains an 8-elements leaky-wave waveguide array, a 1-8 port power divider, and eight high power phase shifters. The gain of the leaky-wave array is 29.6 dB, and the aperture efficiency is 70%. The divider first converts the TM01 mode of circular waveguide into TE01 mode of rectangular waveguide, then divides the input power into eight ports with cascaded power split waveguide branch. Differences between the output ports are less than 0.16 dB, the power handling capacity is 1.1 GW. The phase shifter is realized by changing the width of the rectangular waveguide with a flexible brass reed, the power handling capacity is 150 MW per shifter when it works under vacuum environment. The beam scanning angle of the antenna system is ranged from -40 to 40 with a gain loss of -3 dB as simulation result shows.