1. A speech recognition system for a mobile terminal, the system comprising: an acoustic variation channel unit for transforming a speech signal into feature parameters and Viterbi-decoding the speech signal to produce a varied phoneme sequence by using the feature parameters and predetermined models; and a pronunciation variation channel unit for Viterbi-decoding the varied phoneme sequence to produce a word phoneme sequence by using the varied phoneme sequence and a predetermined DHMM (Discrete Hidden Markov Model) based context-dependent error model.