The application provides a reactive power compensation optimizing configuration method and a reactive power compensation optimizing configuration system. A problem of transient voltage instability in an electric power system is solved from an angle of dynamic reactive power compensation according to low voltage maintenance time of each node in each fault condition. An optimal compensation place and optimal compensation capacity can be obtained via two optimizing models established by the reactive power compensation optimizing configuration method and the reactive power compensation optimizing configuration system, a global optimal compensation result is obtained, and system operation safety and stability are ensured.