Abstract: Because of nonuniform distribution and irregular arrangement of fibres in the composite lamina,the foundamental difference betwean fibres(or matrix) in the lamina and separate bundles of fibre (pure matrix),the difficulty of determining elastic properties of a separate bundle of fibre by experiments, the problem of determining the elastic constants, E₂,G₁₂,G₂₃,v₂₃,etc.,by micromechanical method has not been solved very well,althouth it has been discuseed for many years.All of the available mixture laws have some faults.Under some conditions the results given by these laws are relatively near to experimental results, but under other conditions they are not.To get valuable and relatively simple semi-emprical formulas, it is necessary to tempera and analyse various formulas based on different models.