The invention discloses an SDN-based network derived alarm filtering system and method. The system includes an SDN controller, a first virtual machine, a current divider, a fault detector, a second virtual machine, at least one OVS virtual switch and a display terminal, wherein the SDN controller is configured to receive alarm information, filter the alarm information sent by the OVS virtual switch according to the non-failed OVS virtual switch information sent by the fault detector, and send the unfiltered alarm information to the display terminal; and the fault detector is configured to verify the fault condition of the OVS virtual switch through which a transmission path passes. According to the technical scheme provided by the invention, derived alarms can be effectively filtered, andthe problems of low fault positioning efficiency and difficult operation and maintenance in a traditional network can be solved.