In order to further maintain the quality of sea-fish after harvest, it is necessary to figure out the heat transfer law during its cryogenic freezing and cryopreservation process (below -40℃). There is little literature to discuss thermo-physical properties of food in cryogenic temperature. In this paper, the thermo-physical properties of sea-fish were measured experimentally. A special cold head of pulse tube cooler was designed to measure the thermal conductivity of sea-fish. Then the specific heat was measured through a cryogenic differential scanning calorimeter (DSC). According to the properties of different fishes in sea, the functional relationship between thermal conductivity or specific heat and temperature is put forwarded respectively.