Abstract: A generalized method of cells is often used in the micromechanical analysis of composites. Large number of unknowns and lower computational efficiency are the shortcomings of the original generalized method of cells. Here, the original method is improved by a refined generalized method of cells of which unknowns are subcell tractions in this paper. The influences of fiber shape/arrays, interfacial elastic properties/geometric dimension, inclusion and voids on elastic constants of unidirectional composites are studied by the presented model. Higher computational efficiency, accuracy and universality have been demonstrated in comparison with other methods and experimental data. The presented model has refined discretization, overcoming the shortcoming of an original generalized method of cell that can’t analyze a complex micro-structure. It is expected to provide a powerful tool for the macro/micro multi-scale damage analysis that will be achieved by introducing damage mechanics into the presented model.