In this paper, terahertz spectroscopy technique was used for the investigation of human renal cancer by comparing the response of tumor tissue and normal tissue adjacent to tumor. Based on the measurement and analysis of fresh tissue and lyophilized tissue respectively, the absorption coefficient and refractive index from 0.2 THz to 1.2 THz were obtained. The result shows that water content of biological tissue has great influence on terahertz wave absorption signal amplitude. Meanwhile, difference of cell structure and composition also affect the transmission of terahertz signal. For example, as the different structure and composition of the cancer and normal cell, the absorption coefficient and refractive index of these tissues are completely different. The result indicates that terahertz spectroscopy technique is an important technology and has a broad prospect of application in biological tissue investigation and clinical medicine such as tumor disease diagnosis.