A link fault detection method includes sending, by a first network device, data traffic to a second network device by using a plurality of first label switched paths (LSPs). The method also includes determining, by using each of the plurality of first LSPs within a preset period, whether a first link detection packet from the second network device is received. The method further includes determining an LSP of the plurality of first LSPs for which the first link detection packet is not received as a first faulty LSP. The method additionally includes calculating a first unavailability of the plurality of first LSPs based on the first faulty LSP. The method also includes triggering the plurality of first LSPs to stop transmitting the data traffic according to the first unavailability of the plurality of first LSPs.