A fluorine-containing composition represented by formula (I) ##STR1## wherein X represents a group containing a polyfluoroaliphatic group having from 3 to 26 carbon atoms; R represents a hydrogen atom or an aliphatic group having from 1 to 3 carbon atoms; n represents an integer of from 2 to 3; p represents an integer of from 1 to 100; and Y represents a group represented by formula (II) or formula (III) ##STR2## wherein R represents a hydrogen atom or an aliphatic group having from 1 to 3 carbon atoms; n represents an integer of from 2 to 3; and Z represents an iodine atom, a sulfonate group, or a sulfate group, ##STR3## wherein R represents a hydrogen atom or an aliphatic group having from 1 to 3 carbon atoms; n represents an integer of from 2 to 3; and Z.sup.1 represents an iodine atom, a bromine atom, a chlorine atom, or a hydroxyl group; and a process for preparing the same.