— In this work, we proposed a reliability-based enhancement for the Viterbi and the optimal decoding of the convolutional tailbiting codes (CTBC) from the observations that the decoding does not have to start from the beginning of the received codeword, and that the reliability of the received vector can be used to determine a good starting position of the decoding process. Our reliability-based enhancement improve the performance of the Viterbi-based algorithm and the optimal algorithm either in error rate or in complexity. Simulation results show that our algorithms has lower complexity than the previous algorithms without Word-Error-Rate performance sacrifice.