The different surface mucus from human normal and cancerous intestinal tissues were investigated by terahertz time-domain spectroscopy technique and the absorption coefficient and refractive index were obtained in the range from 0.2 to 0.8 THz. The study found that the terahertz absorption intensity of fresh normal mucus is close to water, which indicating that the water in fresh tissue occupies the main contribution. The cancerous samples showed higher absorption coefficient and refractive index than that of the normal samples. It suggests that terahertz spectroscopy possesses the capability of identifying the cancerous tissue which has great potential application prospect in biological detection and tumor disease diagnosis.