Abstract: With the asymptotic homogenization theory , a novel digitized cell- based finite element method (DCB-FEA) is presented to simulate the constitutive properties of composite materials. In this method , a three-dimensional (3D) unit cell model to represent the actual geomet ry of the microst ructure is converted into a raster graphic by3D scan-conversion algorithms , and then directly interpreted to be a finite element model. Since all the elementshave the regular shape and the same size , the number of element stiffness mat rices actually needed is reduced to thenumber of materials. Furthermore , only the material IDps of each element s need to be stored ; the other geomet ry information of the FE mesh , e. g. , the number of nodes and elements , element connectivities , and node coordinatevalues , can be automatically evaluated only if necessary in the computation. Otherwise , even the periodic boundarycondition can be easily determined because the position of each boundary node is fixed. In the DCB-FE modeling ,much more element s than usual are used with an improved resolution , especially for 3D cell models. This leads tohuge memory required to store the result . So the element-by-element FEM with a preconditioned conjugate gradientmethod is utilized to avoid const ructing the global stiffness mat rix. Finally , numerical test s of 3D composite st ructure were conducted , and more accurate result s of the effective modulus were obtained.