In order to further explore the influence of sleeve installation structure on internal flow field and separation efficiency of oil and gas separator of screw compressor,PumpLinx software was used to simulate the two-phase flow field with or without sleeve and with different sleeve arrangement structure.By comparing the pressure change curves before and after installing the sleeve device,it is found that there is little difference in the pressure change with or without the sleeve device,indicating that the sleeve does not cause excessive loss to the compressor power.By comparing the flow field distribution diagram and velocity vector diagram of the sleeve upright,inverted and unmounted,it is found that the sleeve placement has obvious effects on increasing collision,reducing turbulence and integrating flow field.Further analysis shows that the upright arrangement has better impact and rectification effect than the inverted arrangement,and the conclusion is drawn that the up-facing sleeve at the inlet of the oil and gas separation cylinder can improve the oil and gas separation efficiency.It provides reference for further optimization of the structure of oil and gas separator.