The invention is concerned with the method and the equipment that uses the redundancy overhead of the virtual cascade connection to insert error correcting code in order to improve the fault tolerant capability of the virtual cascade connection. It is; conquers the shortage in the existing technology that the multiframe state machine requests strict to the correctness of the multiframe number, not easy to recover after make a mistake, and leads the lower capability of the virtual cascade connection; the method is: the sending end uses reserved bit in the multiframe to insert error correcting code, and processes fault tolerant process at the receiving end, recovers the correct multiframe. The invention also provides the multiframe sequence number fault tolerant equipment, includes: the error correcting code insert module and the error correcting code processing module. The invention is low cast, compatibility with inhere protocol, high stability with the virtual cascade connection.