A bi-level optimal dispatching model for an active distribution network considering dynamic reconfiguration is put forward. The optimal functions of both levels are lowest operational cost and best fast voltage stability. The optimal function of the lower level is part of that of the upper level. The coordination optimization is realized by defining the same optimal function of the upper and lower levels. The decision variables of the upper level are grid structure in every reconfiguration period. To improve the calculation efficiency, a decimal encoding method based on fundamental loops is employed. The decision variables of the lower level are the power of distribution generation, the reactive power of capacitor banks and static var compensator, and tap position of OLTC to achieve the optimal dispatching of the active distribution network. The IEEE 33 bus system is employed to verify the feasibility of the proposed method. The simulation results suggest that the proposed reconfiguration method can improve calculation efficiency significantly and the proposed bi-level optimal model can reduce the operational cost and improve the voltage stability of the power system simultaneously. This work is supported by Science and Technology Project of the Headquarter of State Grid Corporation of China (No. 5400-201956447A-0-0-00).