The present invention is directed to a method for producing fluorine-containing oxyalkylene compounds used in a cement admixture represented by the formula (4), which comprises ring opening polymerization of at least one cyclic ether represented by the formula (3) in the presence of an acid catalyst and a fluorine-containing hydroxyl compound represented by the formula (2): R.sup.f --Q.sup.2 --OH (2) ##STR1## R.sup.f --Q.sup.2 --O--(A.sup.2 --O).sub.k --H (4) wherein R.sup.f is a C.sub.1-22 polyfluoroaliphatic hydrocarbon group which may contain ethereal oxygen atoms or thioethereal sulfur atoms, Q.sup.2 is a C.sub.3-5 linear or branched alkylene group, k is an integer of from 1 to 100, and A.sup.2 is a C.sub.2-4 linear alkylene group or a group having at least one hydrogen atom of said alkylene group substituted by a hydrocarbon group which may contain ethereal oxygen atoms.