In view of the problems existing in the traditional centralized power service restoration method a distributed power service restoration method for smart distribution grid is proposed. The method is based on the smart terminal unit (STU) arranged at each measuring point of the distribution grid, and through the information interaction and cooperation between the STU, the power service restoration task is completed. Combined with characteristics of distributed system and requirements of service restoration, distributed management of network topology information, network topology equivalence method, searching method of network topology and the simplified calculation method of the constraint conditions are analyzed and studied. The principle of reciprocating search is put forward, and the determination of the theoretical maximum restoration range and the determination of the scope of the actual restoration are completed. A simplified method for solving the constraint conditions of restoration is proposed based on Thevenin equivalent.