In the present paper,FT-mid-IR fiber optics spectroscopy was used to determine the thyroid tumor.A modified WQF-500 FTIR spectrometer with MCT detector and mid-IR fiber optics ATR accessory was used in this work.Percutaneous examination of the skin overlying the thyroid tumor was performed on five patients,in vivo detection and in vitro measurement of six patients in operation room was also carried out.The experimental data indicate that malignant and benign thyroid tumor could be distinguished from the spectra of percutaneous examination,the in vivo measurement and freshly resected thyroid tissues.The relative intensity and peak position of the IR bands in the region of 1 700-1 500 cm-1(amide Ⅰ and amide Ⅱ),1 480-1 400 cm-1,and 1 320-1 200 cm-1 are reliable spectral marker or indexes for tumor detection.These results demonstrate that FT-mid-IR fiber optics spectroscopy exhibits prospect to develop a novel non-invasive method for thyroid tumor detection.