The utility model discloses a sealing structure of a membrane assembly. The sealing structure comprises a macromolecular separation membrane layer, a non-woven cloth composite layer, a solid glue layer, a secondary non-woven cloth composite layer and a secondary macromolecular separation membrane layer which are arranged in sequence, wherein the non-woven cloth composite layers comprise non-woven cloth and liquid glue permeating into holes in the non-woven cloth. According to the sealing structure disclosed by the utility model, a raw material source of the non-woven cloth can be effectively expanded, the sealing property of a membrane bag is guaranteed, and the selection separation performance of the membrane assembly is improved; the sealing structure is suitable for sealing a flat-plate membrane assembly such as a spiral flat-plate membrane assembly and a plate frame type flat-plate membrane assembly and is particularly suitable for separation on gas components with a high sealing requirement.