Abstract: The model ring systems of cluster (H₅Li)₄ were used to simulate the doped Polyacetylenc, and computed by ab initio restricted Hartree-Fock self-consistent field molecular orbital method.We obtained the changing rules of values such as total energyies, energy levels, bond orders, etc.and thus; explained the changing rules of geometrical structure and band structure, insulator-metal transition and electric conducting mechanism of the doped polyacetylene.