The invention relates to a power electronic compensation device for an electrified railway and belongs to the field of electrified railway power supply. The compensation device for reactive power and non-symmetrical compensation for the electrified railway is characterized in that the device comprises three inverter bridge arms sharing a DC bus and a device detection and control unit, wherein the AC outgoing lines of the three inverter bridge arms are connected to an electric traction system through a connection reactor or a connection transformer; the AC outgoing line of the first bridge arm is connected onto the leading phase of the electric traction system; the AC outgoing line of the second bridge arm is connected onto the lagging phase of the electric traction system; the AC outgoing line of the third bridge arm is connected onto the return cable of the electric traction system; the device detection and control unit is used for collecting and analyzing all signals, and calculating and controlling a device to output compensating current. According to the invention, the dynamic compensation structure of three bridge arms is adopted and the three bridge arms share the same DC bus, so that various compensating currents can be output, and besides reactive current, negative sequence current and harmonic current can also be output directly.