A simple model for DNA molecules is proposed.The dynamical mechanism of the nonlinear localized excitation is studied by Runge-Kutta method.The large amplitude motion is simulated for N coupling base pairs of DNA molecules.The physical picture of the nonlinear localized excitation and its stable propagation can be emerged by means of adopting suitable parameters of Hamiltonian and time stpe.The nonlinear interaction on the beather effect is also discussed.

In this paper, The statistical laws satisfied by the random force of the Langevin equation in physics are discussed.The Monte-Carlo method is used to simulate the motion of Browian particles in the ha ornic oscillator potential with a computer germinated the Gaussian random numbers.The variation of the solutions of the Langevin equation with time step is studied. A foundation of the numerical calculation for such a problem is provided.