Based on the finite difference method, the factors affecting the temperature distribution along the thickness of plate during cooling process were analyzed. They include heat of transformation, heat conduction coefficient, specific heat, carbon content, cooling time, plate thickness and water flow. These factors form the basis of cooling specifications. In order to ensure the temperature distribution homogenous along the thickness, some cooling strategies, such as, interval cooling, zonal arrangement of header, were applied on line. The on-line results showed that the finite difference method can correct simulate the cooling process and that the structure permanence of the steel improved greatly.