Slot waveguide array antennas are used in many of missile and radar because of their simple structure mixability feature which causes being mixed with the body of many missiles and radiates equipment. This antenna is actually a waveguide which there are some slot arrays located on its wall. The wave inside the waveguide radiates from the slots through the outer space. And the favorite beam is made. The advantages of this type antenna are usage in high power and also low costs of fabrication and also having the ability of electronic scanning and high level of mechanical durability in different conditions. According to the mentioned advantages they are used in many of proximity fuse of many guided missile. Proximity fuse is actually short radar which is located in guided missile and has to detect the targets properly. In this paper, an X band slot array antenna with 20 longitudinal slots on the broadwall of the rectangular waveguide, with a gain of about 18 dB have been designed, simulated and fabricated witch it is suitable for proximity fuse of guided missiles. Finally the results of the test are compared with the results of simulation.