Principal component analysis (PCA) is aimed at explaining the covariance structure of multivariate data by way of reducing the whole data set to a smaller number of independent variables. By means of iso_ion spectrometry, the authors have analyzed 56 groups of trace elements data (Au, Ag, Sb, Cu, Pb, Zn, Sr, Ba, Mn, Co, Ti, Cr) along two sections of Gaojian Group in southwestern Hunan, and explained the geological implications of the calculated results and PCA figures. Components F1 in Section C and Section L have similar information, reflecting the main characteristics of original sediments in the two sections. As for the data of section L, 13 kinds of trace elements data are divided into 5 groups: Co-Zn-Cu(Mn, Ba), Ti-Cr, As-Sb, Au-Pb-Sr and Ag, as indicated in F1-F2 diagram. With regard to the data of Section C, the groups of variables are not identified very well. As, Cr, Sb and Ti are correlated closely with component F2, whereas Sr is in negative correction with component F2. The processes controlling the distribution of such noble metals as Au and Ag were complex. The oxidization environment controlled distribution of Au in Section L, and the reduction environment was beneficial to the precipitation of Au and Ag in Section C. As sedimentary environments are different, some trace elements in the northern part of the district are obviously different from those in the southern part. According to the squared distance (d k i) 2 of the "noise", the distribution of Ag and Pb was partly affected by the late tectonic movement.