The static and dynamic reconfiguration algorithms for a distribution system based on time interval are proposed. The algorithms are based on the optimal flow pattern and the objective function is the minimum of energy loss during a period of time. A modified calculating method of the optimal flow pattern is presented using the characteristics of the load pattern of distribution system. Then the method is adopted to make the static reconfiguration optimal. The constraint of operation numbers for switches must be considered in making the dynamic reconfiguration optimal. Thus a formula for energy loss reduction is proposed to calculate and estimate the effectiveness of different switch operations. Some effective heuristic rules are also introduced to determine the operating sequence of switches. The proposed algorithms have been proved feasible and effective with the results of a test system.