The normal and malignant human thyroid tissues have been studied by means of Fourier transform infrared spectroscopy( FTIR) , and the results show that some remarkable spectral differences are observed among the two types of the samples. In the normal thyroid tissues, the bands near 1165cm- 1 and 1745cm- 1 are obvious relatively,but the two bands are not observed almost in the malignant tissues. In the malignant tissues the relative intensity of the band near 970cm- 1 is stronger than that in normal tissues, which suggests that the relative contents of phosphoryl- ated protein increase. The intensity of the band near 1080cm - 1 is stronger in the malignant tissues shows that the relative contents ofDNA in cancer cellular increase. The bands of amide Ⅰ and amide Ⅱ are stronger in the malignant tissues than that in normal tissues, and the peak wavenumber of amide Ⅱ ofmalignant tissues is about 2cm - 1 lower. The study shows that the FTIR can be used in the clinic to discriminate malignant and normal thyroid tissues at the molecular level. It is able to provide reliable information for investigation of normal and cancerous thyroid tissues.