The invention relates to a middle-high voltage variable-frequency power source of a novel topological structure. The middle-high voltage variable-frequency power source is composed of a phase-shifting rectifier transformer and a plurality of power units. A secondary side of the phase-shifting rectifier transformer is composed of multiple different phase groups, wherein each phase group is divided into three windings in delta connection. Each phase group is used for supplying electricity to a same group of power units; the power units in the same phase are orderly serially connected and overlapped to form a multi-level structure. All serially connected and overlapped power units in an A phase, a B phase and a C phase are simultaneously connected to a three-phase bridge rectifier transformer in the form of star connection. The power source with high quality and high reliability is provided by the invention.