This paper carries out ab initio calculations to study the 80Se2(X3∑-g)state and 80Se+2(X2∏g),80Se+2(a4∏g)states by using completed active space self-consistent field and multi-reference second order perturbation theory.The electronic curves of these states including spin-orbit coupling are calculated,and then the spectroscopic parameters are obtained.The photoelectron spectra of 80Se2 molecule in gas phase are assigned according to Franck-Condon analysis based on calculated potential energy curves.The ionization energies of 80Se2 molecule are determined by the present calculation.