The invention discloses a power distribution system. The power distribution system is arranged in a case of a server and is used for supplying power for a first mainboard and a second mainboard of the server. The power distribution system comprises a power supply unit, a power distribution unit, a first control circuit and a second control circuit. The input end of the power distribution unit is connected with the power supply unit so as to convert power output by the power supply unit into two paths and to output the power through a first output end and a second output end. The first output end of the power distribution unit is connected with the first mainboard through the first control circuit so as to provide power for the first mainboard. The second output end of the power distribution unit is connected with the second mainboard through the second control circuit so as to provide power for the second mainboard. According to the invention, the first control circuit and the second control circuit are respectively used for controlling connection and disconnection of a power circuit between the power supply unit and the first mainboard and connection and disconnection of a power circuit between the power supply unit and the second mainboard, so that the electricity is used reasonably.