Abstract: The reliability of the flexible DC converter station, a key sector in the flexible DC transmission system, directly affects the operation level of the flexible DC transmission system. Firstly, the topology analysis and the equipment classification of the FDC converter station are carried out, focusing on the key equipment. For the converter valve, the sub-module fault state transfer process is analyzed by combining the reliability block diagram and the Markov process. As to the hybrid DC circuit breaker and the converter transformer, the multi-level deterioration states, the fault and maintenance states are taken into account. The health index theory and the Weibull distribution are combined to obtain a time-varying failure rate model considering the state differences and the reliability calculation is carried out based on the Markov process. Based on this, the partitioning of the flexible DC converter station is carried out and the energy availability of the flexible DC converter station as a whole is calculated by a universal generating function using a combination of the multiplicative operators. The decision of the condition maintenance is performed by taking the energy availability rate as the optimization objective, which is to be converted into outage losses, and the maintenance mode and the inspection period as the decision variables. One example based on a demonstration project in which the reliability of the key equipment and the overall reliability parameters of a straight converter station are calculated and analyzed. The changes in the energy availability and the outage losses of the station are compared and analyzed for different maintenance methods and inspections.