Speech Recognition and Verification are important components of a Keyword Spotting System whose performance is determined by both of them. In this paper, a new model-distance based utterance verification algorithm is proposed to improve the performance of the keyword spotting system. Furthermore, a substitution-error recovery module is built for improving of the system, which enhances the detection rate with the false-alarm rate remaining almost the same. Experiment shows that with the novel utterance verification method and new added substitution-error recovery module, the system performance is improved greatly.