This paper conducts the experimental study on the performance of steamwater twophase flow device composed by a nozzle,mixing chamber and the corresponding valves when the inlet steam pressure is in the range of 0.18~0.22 MPa．The experimental results show that the injector can run stably and reliably and the temperature of outlet water is increased obviously in low inlet steam pressure．This characteristics can be used as effective heaters in the engineering fields such as power plants,heating,the light industry, etc． When a singlestage ejector can not meet the requirements of heating conditions, doublestage ejectors can be used.