In the present paper, lyophilized sera from 31 patients with colorectal cancer, 8 patients with enteritis and 10 healthy controls were measured using Nicolet Nexus-670 Fourier Transform Infrared (FTIR) spectrometer, and the spectral features were investigated and comparison among three groups was made. The result showed that (1) there are 11 peaks of absorption in the spectrum of lyophilized sera, the wavenumber of the ninth peak moved to 1 249 cm-1 in the colorectal cancer group and significant difference was observed with the control group (Z=-2.051, P<0.05); Five ratios of absorbance were calculated and no significant difference was observed among three groups; (2) spectrum in the region of 1 700～1 000 cm-1 was analysed with the method of hierarchical cluster analysis and showed only partial success in distinguishing the three groups; (2) spectrum of amide Ⅰ peptide (1 700～1 600 cm-1) was deconvolved to get the percentage composition of protein secondary structures, and no significant difference was observed among three groups. The results provide a preliminary theoretical basic for using FTIR spectrum of lyophilized serum for the early diagnosis of colorectal cancer.