The optical properties of porcine liver were studied during the dehydration process at different constant temperature (37°C, 40°C,43°C, 46°C, 50°C). Each time after porcine liver samples were placed in thermostat for a different period, the weight of samples were recorded by a precise electronic scale, and the optical properties of corresponding samples were measured by a double integrating sphere system. The results showed that the absorption coefficient mainly depended on dehydration level of tissue. In contrast, the reduced scattering coefficient had more complex relation with the dehydration process, which depended on both temperature and heating time. There is not obvious relation between the reduced scattering coefficient and dehydration level. This study implies that dehydration, temperature and teim are important factors altering optical properties of tissue.