The electronic structures of the C60, (H3P)2Pt(η2-C2H4) and (H3P)2Pt(η2-C60) are calculated by using the EHMO method with the fragment analysis. We have modified the EHT parameters so as to yield the orbital energy level correlation and to fit the optical transition gap to the previous theoretical results of C60. In Pt-derivatives, our FMO results with the modified parameters show that the carbon-carbon double bonds of C60 and ethene react like those of electron-poor arenes and alkenes, and also that C60 is more electron-susceptive than C2H4.