The antenna servo system is a key part of CINRAD/SA weather radar, which works continuously and has complex circuits, so it has a relatively high failure rate in CINRAD/SA radar, especially code jumping malfunction. Conclusions are obtained from 68 cases acquired from nationwide CINRAD/SA radar stations by the project team. The code jumping may be caused by the motor, resolver, collector ring, encoder, fiber link, and digital control unit. Combining with the flow direction of antenna angle codes in the servo system and the parameter characteristics of key components, an analysis is made of the factors that lead to jumping codes, and the method to diagnose jumping codes is summarized. In addition, five representative cases are analyzed. According to the statistics of sample fault attribution, some recommendations for the time sequence of component checking in code jumping failure are given, which provides guidance for removing such malfunction quickly and has a beneficial reference for other Servo faults.