Abstarct: The goal of this thesis is designing, simulation and fabrication of slot array antenna at S-band to used in high power microvawe in center frequency equal to 3 GHz. slot array antennas are used widely in radar, space, navigation and etc. application due to their advantages such as low loss, ease of fabrication. In this thesis early to express history of these antennas and how to enter the industry and so express the general information of this antennas and so express review overview in the field of slot array antenas and then by use a new method designing and simulation a slot array antenna in S-band and under the waveguide WR-284 and by fullwave software CST that provide all technical specification,