Abstract: Supported carbon membranes were prepared using phenolic resin as the carbon precursor and porous graphite as the support. The support was impregnated with the resin solution, dried, cured and carbonized to obtain a membrane layer. One-time coating cannot effectively reduce the number of defects in the membrane. Repeated impregnation cycles to add more carbon layers, using a slow cooling rate during carbonization, performing carbonization at a low temperature and short time (500℃ and 10 min), and coating the supported membranes with permeable polymers were used simultaneously to reduce the population of defects to a certain extent. As a result, gas separation selectivity of the membranes was significantly increased