A detailed instruction about the CINRAD/SB digital Servo Control power structures and the antennastate signal process is made, and three reasons are discussed for the CINRAD/SB servo poweroff failure: the protective poweroff of the air switch resulted from overloading, abnormal poweroff signals of the server systems, and abnormal temperature induced by the overflow of the brake. The analysis methods and diagnosis process of that the CINRAD/SB servo system poweroff failure are summed up, and the detailed explanation is given about how to find out and get rid of the faults in two complex cases of the CINRAD/SB servo system poweroff failure and the methods for restoring radar operation in emergency case without spare parts available by making full use of the existing facilities according to the features of the radar lines.