Steam injection boiler is one of the main power and energy consumption equipments in oil thermal production. Generally, the high temperature saturated water enthalpy which is separated by the steam separator is used through the heat exchanger. However the water treatment system of the steam injection boiler is so simple and the separated saturated water is rich in calcium，magnesium and other ions which are easy to foul pipe surface and affects the heat transfer efficiency of the heat exchange equipment. Comparing with the case of no using the equipment, the screw expander which is of a selfcleaning ability recycled the waste heat of the saturated water, which can improve the thermal efficiency by 10.2% and save about 4.56×107 kW·h amount to 18 422.4 t of standard coal in the service period. The effect is significant.