Abstract: Due to the space restriction,half-height waveguide was used in the design of Ku band space-borne waveguide slots array antenna.Ansoft HFSS and Fortran programs were utilized to design the high radiation efficiency antenna consideration of higher order mode influence and mutual couplings among the slots.The test results of a 8×10 slots array antenna showed that the bandwidth of the voltage standing wave ratio(VSWR)below 1.3 was 340 MHz.The NSI near field testing system was used to measure the antenna patterns,the side lobe level was-29 dB in E plane and-27.5 dB in H plane.Good measurement result indicated the availability of the whole optimization design and characteristic curves obtained by HFSS such as equivalent admittance,resonant resistance etc.All of these provided a valid method for the later large antenna design.