The distribution system is the downstream of a power system, which is used to provide high reliability and quality electricity service for customers. Because of the wide area with voluminous facilities, involves in a distribution system, the preventive maintenance of distribution system components is important for the distribution system. For a fault contingency, the utility company has to identify the fault location to isolate the fault and to restore the electricity service for the un-faulted but outage area as soon as possible to enhance the service reliability. With the advancement of compute technology, the distribution automatic system (DAS) has been applied to solve the fault contingency problem by integrating the geographic information system (GIS) real time database (RTDB) relational database with master station and communication systems for the monitor and control of distribution systems. To achieve the function of fault detection, isolation and restoration (FDIR) of distribution automatic system, the FDIR software has been developed with C++ platform. By retrieving the distribution system components in GIS, the Topology processor is applied to identify the connectivity of distribution network. When a fault occurs, the fault flags will be generated and retrieved from the field feeder terminal unit (FTU) according to the states of fault flag and network configuration, therefore the fault location is identified very quickly. After isolate the faulted section, the feeder circuit breaker is closed to restore the upstream service. Based on the loading levels of supporting feeders, the downstream restoration is therefore obtained by closing the normal open switch, besides the application software can also be used to derive the optimal switching operation for loading balance of distribution feeders to enhance the operation efficiency of distribution systems.