Since the finite element method(FEM) was introduced to the orthopaedic biomechanics, it has been applied with increasing intrest to investigate bone, bone-prosthesis, and fracture fixation device, etc., in terms of stress, strain, force, and displacement. The authors implemented the FEM for the "intact" and the "fractured long bone models respectively to observe the mechanical behaviors of the plate fixation for the long bone fractures, and we observed the followings;l. In the intact model, stresses are evenly distributed and smoothly changed. 2. The maximum equivalent von-Mises stress in the fracture model is higher than that in the intact one. 3. Stresses on the plate are much higher than those on the bony surface in the fracture model. 4. Stresses for the bony surface beneath the plate in the fracture model are much lower than those in the intact model;however, stresses are highly concentrated around the screws. 5. Although two-thirds of total compressive load is transmitted through the fracture site area, maximum von-Mises stress in the fracture site is much lower than that in the plate. 6. High stresses are found at the areas between the plate holes and the screw heads. 7. Shearing forces of the screws are higher at the near and end screws from the fracture site.