Previously. TCM decoder has been using the Viterbi algorithm that was complex. In order to reduce the complexity of decoder. we proposed the “modified decoding algorithm using the path back method” and the modified decoding algorithm which extends the previous decoding algorithm to be able to applied to TCM decoder in this paper. On the gaussian and impulsive noise channel. Monte-Carlo simulation is used for analyzing the TCM performance and proving the efficiency of proposed decoding algorithm.