The system of the basic Hidden Markov Model (HMM) algorithm includes the three important algorithms of Baum-Welch algorithm, Forward-Backward algorithm and Viterbi algorithm. The Inv-viterbi problem and its corresponding algorithm is put forward in the paper after the research of the new HMM problem and algorithm. Then a new algorithm system and a new evaluation system are built by introducing the Inv-viterbi algorithm into the HMM basic algorithm system. Finally we give ...