The condition-based maintenance (CBM) is an advanced maintenance program that recommends optimal maintenance policy based on information collected through condition monitoring techniques. At present, CBM was paid attention to widely. The paper theoretically discussed the structure of a complete CBM system based upon the combing and analysis of the current large numbers of literatures of CBM. Firstly, CBM is introduced. Secondly, the three main stages of CBM work process is given. Finally, the basic structural frame of a complete CBM system is designed and constructed according to a series of functions CBM system should implement.