Abstract: The grating lobes of the azimuth scanning angle of a 2-dimension active phased array for space borne synthetic aperture radar (SAR) applications are studied, with the subarray technology used in the array. The grating lobes peak level is reduced by means of tiles arranged into a staggered grid with the manufacture convenience taken into account. The optimized array illuminates that the peak grating lobe level is suppressed effectively. It is important to improve the image quality of the space-borne SAR applications.