Abstract: This paper presents an initial value solution of static equilibrium differential equations of the thin-walled composite laminated box beams considering both shear lag and shear deformation, which is used to establish the related element stiffness matrix and equivalent nodal forces vector. The analysis of the thin-walled composite laminated box beams is admitted into the program system of the matrix-displacement method.The present procedure can be used to analyze effectively the mechanical behaviors of some complex composite structures, such as continuous laminated box girders or laminated box beams with varying cross section, etc.