A method for detecting a mismatch fault in Provider Backbone Bridging-Traffic Engineering, PBB-TE, infrastructure segment protection, comprising: configuring a protection segment on a working segment of a PBB-TE tunnel to protect the working segment, wherein the working segment and the protection segment compose an Infrastructure Protection Group, IPG; configuring a Traffic Engineering Service Instance, TESI, which is a channel for forwarding a Connectivity Check Message, CCM, on the working segment, and initiating a point-to-point Maintenance Association, MA, on the TESI, wherein two Maintenance Endpoints, MEPs, of the MA are two endpoints SEP of the working segment; when endpoints of the IPG, Segment Edge Bridges, SEBs, finding out egress ports values of the TESI protected by the IPG in Forwarding Databases, FDBs of the SEBs, setting a Present Traffic in Segment, PTS, variable of the MEPs whose egress ports correspond to the egress ports values of the TESI present in the FDBs as true; wherein the FDB comprises destination address and a Virtual Local Area Network Identification VID of the TESI protected by the IPG and a corresponding egress port; and setting a value of a PTS field included in the CCM, according to the value of the PTS variable of the first MEP; and sending, by the first MEP, the CCM including the PTS field to the second MEP; receiving, by the second MEP, the CCM from the first MEP; when the value of the PTS field included in the CCM does not coincide with that of the PTS variable of itself; setting, by the second MEP, a first mismatch fault indication variable mmCCMreceived as true; and when the first mismatch fault indication variable mmCCMreceived remains true after a first preset time period expires, detecting that a mismatch fault occurs. configuring a protection segment on a working segment of a PBB-TE tunnel to protect the working segment, wherein the working segment and the protection segment compose an Infrastructure Protection Group, IPG; configuring a Traffic Engineering Service Instance, TESI, which is a channel for forwarding a Connectivity Check Message, CCM, on the working segment, and initiating a point-to-point Maintenance Association, MA, on the TESI, wherein two Maintenance Endpoints, MEPs, of the MA are two endpoints SEP of the working segment; when endpoints of the IPG, Segment Edge Bridges, SEBs, finding out egress ports values of the TESI protected by the IPG in Forwarding Databases, FDBs of the SEBs, setting a Present Traffic in Segment, PTS, variable of the MEPs whose egress ports correspond to the egress ports values of the TESI present in the FDBs as true; wherein the FDB comprises destination address and a Virtual Local Area Network Identification VID of the TESI protected by the IPG and a corresponding egress port; and setting a value of a PTS field included in the CCM, according to the value of the PTS variable of the first MEP; and sending, by the first MEP, the CCM including the PTS field to the second MEP; receiving, by the second MEP, the CCM from the first MEP; when the value of the PTS field included in the CCM does not coincide with that of the PTS variable of itself; setting, by the second MEP, a first mismatch fault indication variable mmCCMreceived as true; and when the first mismatch fault indication variable mmCCMreceived remains true after a first preset time period expires, detecting that a mismatch fault occurs.