This work proposed and optimized a three-stage membrane process for CO2 separation. The results of this study revealed that the membrane technology is a suitable process for the CO2 separation in a higher concentration. In addition, the MATLAB was used to simulate and obtain the optimal operational parameters for a three-stage membrane process. This work established a partial cycle and recovered the CO2 from the permeation side of second-stage membrane that enhance a higher purity CO2 gas stream. The results of this study indicated that when the CO2 concentration was higher than 50% and at a flow rate of 100000 Nm3 d–1, the CO2 separation could be achieved at the optimal operation condition. Under the conditions that the membrane areas were 2400, 3800, and 1800 m2 for the first-, second-, and third-stage membrane, respectively and the operational pressure at first- and third stage membrane were 3.0 and 2.5 MPa, respectively, the CO2 separation fraction was higher than 90% and CH4 loss rate was lower than 5%. The results of this study have a high potential for the practical application.