The supermolecular structures and erystallization behaviors of FEP copolymer were studied by small angle light scattering technique，microscopic observation and differen-tial scanning calorimetry respectively．The results obtained shows that the morphology of FEP copolymer is critically dependent upon the melt temperature．When the

melt held at temperature below 315—320℃ and began to cool at constant cooling rate．the scattering pattern obtained was circularly symmetric and can be assigned as randomly arranged lamellas morphology．When the melt held at temperature above 315—320℃．the scattering pattern for spherulites was obtained．With the increase of melt temprea-ture，the size of spherulites increases，which can be confirmed by optical microscope study，these results can be best interpreted in corelation with crystallization curves measured in the DSC runs which also have distinct changes at the tran ition temperature (315—320℃)．It appears that in the melt there exists some order regions．which act as nucleus of crystallization and may be destroyed at the transition temperature．The ef-fects of molecular weight and cooling rate on the types and sizes of morphology were also investigated．