Recently increasing energy consumption and subsequent increase of emissions from fossil fuel combustion have caused major enviromental problems in the world. As reported in literature, about three quarters of carbon dioxide increase is due to fossil fuel combustion, therefore to avoide of greenhouse gases emissions especially carbon dioxide, has become an important concern in industries. In recent years, membrane processes have shown high potential to be replaced conventional CO2 separation processes from gas streams. No phase change, low energy consumption, small scale of membrane systems, no waste streams, easy operation, compatibility with environment and low capital and operating cost propel researchers to apply this novel technology. In this study, a review of conventional membranes in separating of carbon dioxide from the gas streams is done and the performance of membranes are compared using the trade-off curves. It is shown that silica membranes have higher performance compared to other conventional membranes.