Starting from the extensional discrete model SSH Hamiltonian containing an external Coulomb potential arising from interchain charged solitons and the counterions, the intrachain electron-electron interaction, the energy spectra and electron states of soliton lattice have been studied in trans-polyacetylene. The results show that: two bound states have been found at the bottom of valence band and several other states at the top of conduction band. With the increasing of the dopant concentration, the localization of bound states are weakened and the discrete soliton energy levels in the forbidden band move into the soliton band. When the dopant concentration is up to 16.67%，all the discrete electron states of soliton lattice disappear and become extended ones. It is found that the forbidden band width increases and the gap (between the top of the soliton band and the bottom of conduction band) namows with the doping level increasing. Furthermore, the gap (from the bottom of the soliton band to the top of valence band) has a maximum at the critical doping level. Finally, the effect of e-e interaction on the energy spectra of soliton lattice is discussed.