The invention relates to a method for controlling an electrified railway, in particular to a method for controlling an electrified railway traction substation 55kV side static var compensator. A device used in the method comprises a thyristor control reactor (TCR) branch circuit and smoothing FC branch circuits, and the TCR branch circuit and the smoothing FC branch circuits are connected in parallel. The TCR branch circuit and the smoothing FC branch circuits are directly hung below a 55kV bus. The device is connected between a contact line and a positive feeder of an AT power supply system railway traction network. An open-loop control mode and a closed-loop control mode are respectively adopted for the control method according to control targets. On the basis of the key technology of electrified railway traction substation reactive compensation, the characteristic of traction substation power supply is comprehensively considered, the open-loop control mode and the closed-loop control mode are organically combined for using, and different requirements of an electrified railway traction substation on the high-voltage side and an electrified railway traction substation on the low-voltage side are comprehensively considered. The dynamic regulation effect of the static var compensator is brought into play to the maximum, and flexible setting of a set value enables a user to issue the regulation targets conveniently according to self requirements.