The structures and stability of the four isomers of C70H2 have been investigated by INDO methods. It is indicated that the most stable isomers are 1, 9-C70H2 and 7, 8-C70H2, and energy of the former is lower than that of the latter by 16.3KJ. mol^-^1, which is in good agreement with the experimental value and the calculated result of an ab initio method. The electronic spectra of C70H2 have been studied, of which the characteristic absorptions are consistent with the experimental results. The stability and spectra of C70F2 and C70Cl2 have also been studied based on C70H2. It is shown that the sequence of stability for C70F2 is the same as that of C70H2 but different from that of C70Cl2, for which 21, 42-isomer is the most stable one in which two Cl atoms are added to the equatorial belt of C70 by 1, 4-addition. The electronic spectra of C70F2 and C70Cl2 are similar to that of C70H2 except the little difference beyond 500nm.

Key words: STABILITY, ISOMER, INTERMEDIATE NEGLECT OF DIFFERENTIAL OVERLAP APPROXIMATION (IND, ELECTRONIC SPECTROSCOPY