The overall moduli tensor of polymer blends is one of the most important characteristics of microscopic morphology development. This article focused on the analysis of dependence of the moduli on mixer resident time in terms of polypropylene-polystyrene (PP/PS) and polypropylene-polyamide1010 (PP/PA1010) blends. Tensile tests on the PP/PS and PP/PA1010 blends with a series of mixer resident times showed a marked change during the initial mixing stage, which may be due to the evolution of particle size and distribution from inhomogeneous to homogeneous. The two cases of periodic spatial distribution of the identical spherical particles were proposed to model the well-dispersed and slightly aggregating morphologies in the steady state. Based on the micromechanical model, the moduli of polymer blends were calculated by incorporating the influences of spatial distribution and Poisson's ratio of dispersed particles. Theoretical results indicated that spatial distribution should have little effect on the overall moduli in the steady state. Analysis of the blend system PP/PA1010 with and without compatibilizing agent showed good agreement between the calculations and experiments. Because the interfacial properties were not taken into account, the model gave an overestimate prediction for immiscible blends, like PP/PS for example.