Abstract: Based on the theory of jet pump and the law of energy conservation,the basic characteristic equations of a novel dual nozzle jet pump was derived by employing Lorenz mixed loss model. When the velocity ratio V = 1,the theo- retical ideal efficiency of jet pump is 100% ;when 0Kj >Ks . The jet pump basic characteristic equations were completed,and the real basic characteristic curve plotting was drawn. The results show that the pressure ratio P increases while the area ratio R increases,whereas the working range decreases,and the efficient range of jet pump moves left on the curve plotting. The peak efficiency increases at first then decreases with the flow rate ratio M1 ,nonetheless the pressure ratio P decreases with M1 con- stantly. This phenomenon is in accordance with the law of energy conservation. According to the experimental data of the prototype,the optimal area ratio Ropt is 0. 30,the optimal flow rate ratio Mopt is 1. 04,and the peak efficiency is 22． 57% .