The pitching system of a large plate microwave antenna is studied. A truss structure with high strength and light weight is designed as the antenna back frame. According to the index requirements, the mathematical model process is allocated through accurate mechanical calculation to select the structure elements such as motor and reducer. Through the finite element simulation of the key structure and the hardening design of high power microwave, the whole pitch system is further guaranteed to complete the experiment. The load is up to two tons, the rotation speed is 10° per second, and the range of pitch motion is 0°-70°. The positioning accuracy is better than 0.1°. All the parameters can meet the design requirements. The direction pattern of the microwave test is good, and the beam direction meets the requirements.