The Ground Based Augmentation System (GBAS) processes carrier smoothing, integrity monitoring and generates differential corrections which is used for final approach simultaneously. The structure and the processing core of GBAS are briefly presented. In addition, the regular maintenance of the system is introduced and the test method of VDB signal frequency, VDB signal power, VDB SWR and time service signal are explained in detail. The purpose of this research is providing technical guidance for regular inspection and maintenance of GBAS equipment