The invention discloses a traction power supply over-zone fault location method for a high-speed railway. When a traction power supply mode is switched from a normal power supply mode to an over-zone power supply mode, an over-zone isolation switch located in a section post of a current power supply arm changes from an opening position to a closing position, the section post sends out an over-zone power supply alarm to a dispatching end, and after the confirmation of the over-zone power supply alarm, the dispatching end remotely controls the input of an over-zone soft strap of distance measuring equipment located in a traction substation, an AT station and a section post and reads over-zone power supply operating parameters. By automatically switching the distance measuring equipment to the over-zone operating state remotely, the method of the invention reduces the manpower, materials and time required for the over-zone setting of the distance measuring equipment, has applicability to various kinds of over-zone power supply conditions and greatly improves the reliability of the traction power supply.