1. A method for utterance verification adapted to verify a recognized vocabulary, wherein the recognized vocabulary is obtained by performing speech recognition on a feature vector sequence according to an acoustic model and model vocabulary database, wherein the feature vector sequence comprises feature vectors of a plurality of frames, wherein the acoustic model and model vocabulary database comprises a plurality of model vocabularies, wherein each of the model vocabularies comprises a plurality of states, and wherein the method for utterance verification comprises: processing a log-likelihood score obtained from speech recognition by taking a logarithm on a value of a probability of one of the feature vectors of the frames conditioned on one of the states of each model vocabulary; generating a verification score based on a processed result; and comparing the verification score with a predetermined threshold value, so as to reject or accept the recognized vocabulary.