Abstract: According to the B3LYP density functional theory, the 6-31 G* basis set was employed to study the equilibrium geometrics and electronic structures of six lower-energy isomers of fullerene C100 and its derivatives C100X4 (X=H, F, Cl, Br) which are based on lowest energy. The calculation results indicated that the D2 C100 isomer is of the most stable structure and the reactions of C100X4 (X=H, F, Cl) are all exothermic. The calculated results of vibration frequencies showed that the four structures of C100X4 (X=H, F, Cl, Br) molecules are all the stationary points on their potential energy surfaces. The C100 F4 is more stable in the molecular cluster investigated, and it is quite possible to be synthesized experimentally.