Based on the generalized Hamiltonian system theory, a new approach to dissipative Hamiltonian realization of nonlinear differential algebraic system is proposed in this paper, and a simple control strategy to stabilize the dynamic system without linearization treatment is designed. The new approach is applied to the nonlinear excitation controller design of structure preserving multi-machine power system. Simulation results demonstrate that the approach proposed in this paper is correct, and the control strategy designed is effective.