Abstract: Quantitative analysis of fricative quality is an important branch of the study of phonemes.The main issue is to search valuable acoustic parameters.This paper conducts the research on the six fricatives of Putonghua with the analysis of spectral principal components.The method is applied to compute the principal components among 162 variables which are the intensity of sound at different frequency between 2,000 Hz and 16,000 Hz.The result demonstrates that three principal components are sufficient for presenting fricative quality.And the effect is 94.786%.It is found that the factor scores based on the principal components can be used to describe the fricative system of Putonghua in a three dimension reference frame.And it is also found that the high frequency principal component is related to the articulating place.And the phonemesis the most typical one among the six fricatives of Putonghua.