Zeolitic imidazolate frameworks (ZIFs) have attracted great attention due to their potential applications in gas adsorption, catalytic membrane reactors, chemical sensing and gas separation. To achieve the massive industrial application, a number of attempts have been made to prepare supported-ZIF membranes. We successfully synthesized a well-intergrown continuous ZIF-8 membrane on the outer surface of silicon nitride hollow fibers by a one-step hydrothermal method. Through controlling ZIF-8 nucleation and growth rates, the membranes were compact and well-coated. Single gas permeation of H2, N2 and CO2 at 25°C, 0.25MPa indicated the sieving behavior of the obtained membranes. N2 permeance did not change with permeation time, while H2 permeance increased in the beginning and keep steady at 8.35×10−7mol/m2Pas due to the high storage properties of ZIF-8, and CO2 permeance decreased in the first hour, then maintained at 1.15×10−7mol/m2Pas due to the strong CO2 adsorption in the ZIF-8 and the cooperative interactions of adsorbed CO2 molecules with CO2 passing through. The H2/CO2 separation factor of 11.67 could be achieved in the separation of 50%H2/50%CO2 mixture.