The automotive power steering units must be taken performance test after they are integrated assembly and then left the factory if it is qualified.Because its internal flow channel is very complicated and the residual hydraulic oil can not be eleminated clearly.So we can set up a 3D model flow channel based on CATIA and use FLUENT software to analysis the key flow channel ,analysing it's pressure distribution and velocity vector diagram then get the real reasonable resluts ,which can provide the basic for the ejector designing