The invention provides a method for obtaining 1,1,1,3,3,3-hexafluoroisopropyl methyl ether through a gas phase methylation reaction of 1,1,1,3,3,3-hexafluoroisopropanol and dimethyl carbonate in the presence of a methylation catalyst, wherein the methylation catalyst comprises a molecular sieve and at least a cocatalyst selected from Cr, Al, Ni, Co, Fe, La, Zr, Zn and Mn. According to the invention, the preparation method has advantages of high conversion rate, high selectivity, environmental protection in operation, easy achieving, easy continuous large-scale production and the like.