The present invention relates to the technical field of train power supply and operation control, and provides a three-rail power supply control system for an electrical railway train. Power supply rails in the system are divided into a first power supply rail, a second power supply rail, and a third power supply rail, wherein the first power supply rail, the second power supply rail, and a running rail constitute a three-phase AC power supply loop, and the third power supply rail and the running rail constitute a DC power supply loop. An AC-DC-AC variable voltage variable frequency device supplies power to a train traction motor by means of the three-phase AC power supply loop and current collectors. Frequency modulation and voltage regulation power supply is conducted by means of the AC-DC-AC variable voltage variable frequency device on the ground to achieve train driving and operation control. The DC power supply loop is powered by means of a rectifying device on the ground, and power is supplied to auxiliary electric equipment of the train by means of the current collectors. By changing the power supply mode of the system and optimizing the system structure, the weight and axle load of train-mounted equipment are effectively reduced, lightweight of the train is achieved, and the bearing efficiency of the train is improved, and moreover, automatic control and unmanned driving for train operation are achieved in the most economical way.