CBM is the last phase of diagnosis-prognosis-maintenance, which has arouse wide attention in recent years. A CBM method based on RUL prediction for the multi-component system is proposed with considering imperfect maintenance and spare part management in this chapter. Due to limitations of the special working environment or maintenance technology for some multi-component systems, imperfect maintenance method is more frequently applied in practical engineering application. At the same time, proper spare part management is needed to be scheduled to reduce maintenance time and maintenance cost. The imperfect maintenance model is constructed based on the virtual age rule. Spare parts are managed based on practical maintenance requirements to reduce the total numbers of spare parts and maintenance preparation cost. Maintenance preparation threshold, spare part ordering threshold and spare part number threshold are optimized based on genetic algorithm.