The crystal transformation of poly(vinylidene fluoride)/cyclohexanone solution casting film in the isothermal crystallization was investigated by the determination of change of melting peak. Effects of the rate of solvent evaporation, the constitution and molecular weight of PVDF, and solution concentration on the crystal transformation were considered in this study. The IR results confirm that changes of melting peak are due to the transformation of crystals from α phase to γ phase. In the solution casting PVDF films, one can obtain α phase PVDF crystals with the higher barrier potential energy in comparison to the α phase PVDF crystals from melt casting films. It causes the easy crystal transformation to γ phase during the isothermal crystallization. The barrier potential energy of obtained α form PVDF crystals was also affected by the rate of solvent evaporation, the molecular weight of PVDF, and the concentration of solution. It was found to be significant for the formation of γ phase crystal in the isothermal crystallization. The crystal transformation in copolymers provides γ phase crystal with high barrier potential energy even though the amount of crystal transformation is less than γ phase crystal obtained in homopolymers.