Abstract: In order to explore the influence of jet pipe structure on the flow field of annular jet pump, three-dimensional numerical simulation of annular jet pump under right-angle turn and arc turn was carried out, and the straight section of annular nozzle outlet was calculated and analyzed. The results show that the flow field is unevenly distributed around the nozzle, throat and diffuser in the jet pipe with right-angle turn. The annular nozzle forms a uniform jet in the jet pipe with arc turn, which is conducive to the uniform and symmetrical mixing and energy transfer between the primary flow and the secondary flow, so that the pressure ratio and efficiency are improved under each flow ratio.The performance of the annular jet pump can be improved by setting（0.5～1） times the outlet width of the straight section at annular nozzle outlet, and the efficiency can increase by 1% at the middle and low flow ratio. At the same time, the straight section helps to stabilize the pressure at the nozzle outlet and to reduce the range of the recirculation area near the inlet of the throat and the extent of the pressure drop.The research findings serve as a support for the analysis of the overall flow field of annular jet pump and the design of jet pipe structure.