A pattern-dependent error correction method and system for a code group alignment finite state machine (FSM) are disclosed. A state corrector generates a start-of-stream delimiter (SSD) detected signal to the FSM when the FSM is in an idle state and at least one condition due to a lost SSD signal is met; and the state corrector generates an idle detected signal to the FSM when at least one condition due to a lost idle signal is met. A pattern corrector generates a corrected code pattern {J,K} to FSM when the FSM is in an idle state and at least one condition due to a false idle state is met; and the pattern corrector generates a corrected code pattern {T,R} to the FSM when the FSM is in a data state, a start of stream state or a data error state, and at least one condition due to a false packet end is met.