The isoscaling parameters αeval in the fiissioning systems,i.e.,those extracted from the Evaluated Nucle-ar Data Library(ENDF/B-Ⅷ.0)and the Joint Evaluated Fission and Fusion File(JEFF-3.3),show an obvious dif-ference from simple statistic model prediction where only the symmetry energy plays the dominant role.To explain the αeval as a function of the charge number of the fission fragment,a statistic scission point model is adopted.Our analysis shows that the effects of the shell correction,nuclear shape deformation,and intrinsic temperature of fission fragments are indispensable as well as the symmetry energy.Furthermore,an alternative method for extracting the intrinsic temperatures of fission fragments is proposed based on the isoscaling relationship in fission fragments.The intrinsic temperatures of the light fragments are higher than those of the heavy fragments.