Abstract: The canonic equations of an intense field model are constructed by substituting symmetric difference quotient for partial derivative in Hamiltonian and the numerical solution is found by using square-preserving and symplectic scheme.The result is consistent with theoretical analyses,and shows that the method is successful.It probably overcomes the difficulties that often encountered to intense field model by using conventional difference methods.

Key words: Intense field, canonical equation of quantum system, square-preserving and symplectic difference scheme