The extinction spectrums of particle system contain some information about the particle size and refractive index with total light scattering particle sizing method. In the visible and visible-infrared region, the principal component transform was performed for the extinction spectrums, the first-order differential extinction spectrums and the second-order differential extinction spectrums of monomodal R-R particle system. After analysis and comparison with the Principal Component Analysis (PCA) method, a selection algorithm for the characteristic wavelengths based on the PCA was proposed. This algorithm uses the principal component transform to dispose the first-order differential extinction spectrums firstly, and then regards the contribution rate of the principal component to the first-order differential extinction spectrums at each wavelength as the main criterion by which characteristic wavelengths can be selected. Meanwhile, the boundary wavelengths in the spectrum region are also selected as the characteristic wavelengths. This selection method ensures that the extinction values of selected characteristic wavelengths contain most information about the particle size distribution. The numerical simulation experiments on the monomodal and biomodal R-R distributions were performed in the independent model, which illustrated the validity and feasibility of the selection method based on the PCA.