A combination of membrane separation with gas hydrate crystallization has been proposed for enhancing the efficiency of separation and purification of gass. A mathematical model of a hybrid gas hydrate-membrane method has been derived. The results of calculation of the degree of separation by this method for different process conditions are presented. It has been shown that the use of gas hydrate crystallization in membrane technology can preclude the concentration of impurities in the high-pressure compartment of a membrane element and thereby significantly improve the gas separation and purification efficiency.