A method for processing a forwarding device fault, a device, and a controller are provided, and relate to the communications field. The method is as follows. An SNC receives a notification message sent by a first forwarding device, where the notification message includes a fault parameter of the first forwarding device, and the fault parameter includes a device identifier of the first forwarding device, a port identifier of a degraded port, and a degradation value of the port identified by the port identifier. The SNC determines, according to the device identifier and the port identifier, at least one forwarding path that passes through the port identified by the port identifier. The SNC also determines, according to the fault parameter of the first forwarding device and the fault parameters of other forwarding devices on one forwarding path, whether to update the forwarding path.