The invention relates to a traction power supply system of an electrified railway novel AT power supply mode applying 2 multiplied by 27.5kV outdoor modular appliance, comprising a traction substation arranged at the side of the electrified railway; the output side of the traction substation is connected with an ascending/descending traction network; the middle parts and the tail ends of power supply arms of the ascending/descending traction network are provided with parallel devices with parallel power supply function; an electrical split-phase position between the power supply arms of the ascending/descending traction networks of two adjacent traction substations is provided with a skip zone device with skip zone power supply function; the parallel devices are connected with an AT device; the parallel devices comprise four parallel power supply units which are parallel modules for power supply; and the AT device comprises four integrated AT stations which comprise a first AT transformer, a second AT transformer and a modular appliance used for the AT stations. The traction power supply system has small occupied area, can reduce investment cost, and has high reliability and free of maintenance.