Abstract: Bernoulli Equation shows a principle that there is a greater change of pressure when a high density working fluid is used than a low density fluid under the same change of flow velocity. According to the principle,the study tries to explore the working performance of the ejector refrigeration system,when the working fluid of water is replaced by room temperature liquid metal and high density solution. And the study also tries to improve the performance with the method of changing the structure of the nozzle from a simple one to an inside annular structure,and increasing the distance between the nozzle and the entrance of mixing chamber. Through experiment study it is discovered that there is an important influence on the system performance when high density working fluid is used; there is an obvious improvement of the performance when the structure of the nozzle is changed from a simple one to an inside annular structure; there is a peak point when distance between the nozzle and the entrance of mixing chamber is changed from 5 mm to 13 mm,and the peak point occurs at 10 mm. The study provide an original working performance of different fluids and the experimental phenomena and the results provide a reference on the improvement of ejector refrigeration system,especially on the flow characteristics of liquid metal.