Due to changing channel conditions for the HF (high-frequency) receiver, It is indispensable to track accurately the channel. In the paper, a novel scheme about semi-blind channel estimation and decoding is presented as follows: the bit information (extrinsic) from the channel decoder is fed back to the channel estimation to suppress the ISI (Inter-Symbol Interference) effectively so that the estimation can provide more reliable information to the channel decoder for the next iteration. Through iterations, more reliable information can be exchanged between the estimation and decoder. An ideal performance can be achieved up to remove the ISI completely and an optimally combined signal is provided to the channel decoder with low computational complexity.