Analysis of a variety of engineering problems requires computations at different length scales. A combined discrete/finite element numerical method is proposed and generated to meet this requirement. This method performs discrete element method at meso-scale to reach necessary precision, and finite element method at macro-scale to save the computation time and cost. The key point for this method is to define a special transition layer between the discrete element zone and the finite element zone. This new method is applied to simulate the failure response of a pre-stressed aluminum plate under laser irradiation and find agreement between the computationan result and the experimental result.