Abstract: Based on the stress distribution in representative volume element (RVE) for Hsueh model, the explicit expression of Poisson’s ratio ν_12, which can be reduced to the Halpin-Tsai model, was derived from average approximation method, and it basically coincides with the Bridging model. The modified Halpin-Tsai model for transverse modulus E₂₂ was developed by introducing an exponential decay function of l/a related to the Fu and Giner models, and coincides with the self-consistent model. Based on the assumption of Poisson’s ratio properties, the deduced results better than the Halpin-Tsai model are close to the finite element results for Poisson’s ratio ν₂₃, and then the underestimation of shear modulus G₂₃ was corrected by the modified Halpin-Tsai model for ν₂₃ based on reverse engineering. Based on the laminate analogy approach (LAA) in conjunction with fiber length distribution (FLD) and generalized fiber orientation distribution (FOD) functions, the elastic moduli for two kinds of injection molded short glass fiber reinforced thermoplastics (FRT) composite were predicted. The results show that the four combined micromechanical models all predict the elastic moduli of the composites well, but the prediction results of weight distribution of fiber lengths are more reasonable than that of number distribution of fiber lengths, especially more than 5% in the improvement effect of longitudinal Young’s modulus E_L.