The invention discloses a bilateral power supply system for an electrified railway. The bilateral power supply system consists of adjacent traction power substations, traction nets and a section post, wherein the traction nets and the section post are arranged between the adjacent power substations; the secondary sides of traction transformers of the traction power substations are connected in series with reactors respectively; a circuit breaker in the section post is used for communicating the traction nets on both sides of the circuit breaker to construct bilateral power supply; the sum of the reactance values of the reactors in two adjacent traction power substations is equal to a minimum value required by current balancing of a power system; the ratio of the reactance values of the reactors in adjacent traction power substations to the sum of leakage impedance values of corresponding traction transformers is inversely proportional to the ratio of rated capacities of the traction transformers of the adjacent traction power substations; the traction transformers and the reactors which are connected in series with the transformers can be combined into a more compact high-leakage-reactance traction transformer in order to reduce land occupation of the traction power substations; a neutral section where the section post between adjacent traction power substations is positioned can be eliminated without influencing normal running of the power system, and the technology is advanced and is easy to implement.