Abstract: The static plane product moment method of calculating the displacement of the girder is another method which is similar to the graphical method of multiplication in the books under the condition of a unit force acting on the structure for determined distortion.In case the load is complicated and heavy,the adoption of the static plane product moment method is simple and intuitive.Without plotting the bending moment graph,we are able to calculate the various related displacements and the deformed clastic curves of the determined girder.