The invention discloses a high-speed railroad power supply network system. The system comprises at least two traction substations, an autotransformer (AT) partition post arranged between the two adjacent traction substations, AT posts arranged between the traction substations and the AT partition post and ascending and descending traction network power supply arms connected with the traction substations, the AT posts and the AT partition post, and an ascending feeder breaker 1DL and a descending feeder breaker 2DL of the traction substations are provided with a first impedance protection device and a first overcurrent protection device respectively; each AT post is provided with 2 autotransformers and a disconnector 1GK used for connecting the 2 autotransformers in parallel, two feeder breakers 3DL and 5DL or 4DL and 6DL in parallel on the incoming side of each autotransformer are provided with a second impedance protection device and a second overcurrent protection device respectively, and electric sections are arranged between the contact points of each 2 feeder breakers connected with the corresponding autotransformer and the ascending and descending traction network power supply arms.