This research aimed at exploring the differences of speech spectrum of different phonemes(vowels or consonants) between telling lies and telling truths in the lie scale of Eysenck personality questionnaire(L scale). Because the voice can reflect a man’s emotional and physical state and telling lies may evoke physical arousal, we hypothesized that the speech spectrum during lying and truth-telling would be different. Forty-six subjects completed the Revised Eysenck Personality Questionnaire Short Scale for Chinese edited by Zhonggeng Chen, which has been demonstrated to be reliable and valid for Chinese participants. The inventory contains four personality trait scales: Psychoticism (P), Extraversion (E), Neuroticism (N), and Social Desirability (L). The L scale contains questions on which individuals tend to lie for social desirability, and the scoring standard is the same for everyone. If a participant received a score of one instead of zero on an L scale question, then this response was recorded as a lie. They were instructed to verbally answer the questions shown on a computer screen by E-Prime 2.0 with “yes” or “no”(/shi/ or /bushi/) in Chinese and their responses were recorded by the computer. Praat 5.1.30 software in a Windows 2003 operating system was used to analyze participants’ recorded voice samples. Measured speech spectrum parameters included fundamental frequency, frequency of the former three formants (F1, F2, F3), and bandwidth of the first three formants (B1, B2, B3). We analyzed the speech spectrum parameters of both the consonant /sh/ and the vowel /i/ in the present study because it has been previously demonstrated that the position and motion of oral cavity, larynx and tongue are different between consonants and vowels when they are pronounced. The responses of “yes” and “no” were also analyzed separately in order to control the influences of /bu/ to /sh/ and /i/. Consistent with our hypothesis, Paired Sample t Test showed that: when participants responded with “yes”, the effects of lying were significant or margin significant on F1, F3, and B1 of the consonant /sh/ (p=.074，p=.032，p=.069, respectively); when participants responded with “no”, the effects of lying were significant on F1, F2, and F3 of the consonant /sh/ (p=.037，p=.020，p=.015, respectively); There was not any significant effect of lying on the speech spectrum of /bu/ and the vowel /i/ in whatever kind of responses (all ps > .10). The results of this research indicated that it was effective to distinguish telling lies and telling truths through speech spectrum analysis. In addition, the effects of lying on the speech spectrums of different phonemes may be varied.