Abstract: To improve oxygen-enriching properties of cellulose derivative membranes, trimethylsilyl methylcellulose (TMS-MC) with degree of substitution (DS) of 1.12 was synthesized by using methylcellulose with DS of 1.80 as raw material and hexamethyldisilazane as reactant in a homogeneous reactive system.The chemical structures of TMS-MC were characterized with FT-IR and ¹H NMR.The product samples were fairly soluble in ordinary organic solvents such as tetrahydrofuran, chloroform, xylene, toluene, and so on.The gas separation membranes were prepared by casting a xylene solution of TMS-MC on a sheet of PET.It was found that the oxygen permeation properties of the TMS-MC membrane were improved and an obvious increase in separation factor was obtained especially.Comparing with methylcellulose, for example, the permeability coefficient and separation factor of the TMS-MC membrane increased from 2.5 Barrer and 2.41 to 23.85 Barrer and 5.42 at 20℃, respectively.