Abstract: This paper discussed the speech characteristics of Putonghua voiced initials and the spectrum characteristics of preemphasis, then proposed an algorithm for thte isolation and classification of the initials basing on the measurement of the energy ratio of the speech signal with and without preemphasis. In the classification experiment using all Putonghua syllables with voiced initials spoken by a group of 8 adult speakers (4 male and 4 female) from different provinces of China we obtained an over 98% correct classification rate of the initials into voiced initials and' zero' initials. We also did an initial recognition experiment by applying stepwise linear discriminant analysis and obtained 86% average recognition rate of these initials.