The moleeuar motions of eopolymers of tetrafluoroethylene and perfluoro-4-methyl-3.6-oxa-△7-octyl．sulfonyl fluoride have been determined from --150℃ --80℃ using vibrating reed device．The materials are partly crystalline perfluorinated copolymers containing different amount of side ehains．Four relaxations are observed，labeled a，y1，γ2，and γ3 in order of decreasing temperature．The α-relaxation (room temperature) is assigned to the glass transition，γ1-relaxation (--50℃，215Hz) to hindered motion of main chains，γ2-relaxation( --60℃，230Hz) to side chain motions．The γ3-relaxation (--77℃，260Hz) is assigned to short segments of main chains (CF2)x motions and its intensity increases with annealing．