In this paper, PRO II process software is used to study the membrane separation effect of the low temperature liquid station overhead noncondesnsable gas at Shengli oilfield.Taking the polyimide membrane which is widely used as the object, a single-stage membrane calculation model with a separation scale of 1000Nm3/d was established for simulation and calculation.The effects of secondary compression pressure, inlet gas temperature, membrane area, and osmotic exhaust pressure (supercharge or vacuum) on the osmotic side and high-pressure side products are calculated.The results show that the optimal process parameters are achieved at the secondary compression pressure of 1.6 MPa, the inlet gas temperature of 40 °C, and the osmotic exhaust pressure of 0.2 MPa.The comprehensive performance is good under this condition, and the membrane material is the least used (membrane area of 30m2).The results of osmotic side separation, CO2concentration, CO2yield and high pressure side separation, hydrocarbon concentration, hydrocarbon yield and hydrocarbon calorific value are all optimal.