A refrigeration system in a thermoelectric refrigerating unit was developed,which is mainly used in blood preserving.Through investigations regarding the thermoelectric refrigerator by controlling the working voltage,ambient temperature and condition of heat rejection,the main factors which effect the refrigeration capability of the thermoelectric-refrigerating unit and the best working parameters such as the optimal working voltage,the optimal working current,and the optimal heat emission system for heat sink were analyzed.The minimum temperature in the refrigerator interior that could be achieved was obtained by experiments under different ambient temperatures and optimum working parameters.