In this thesis the changes in the microstructural features such as the morphology, crystallization behavior, and the crystalline structures of the polypropylene(PP)/nylon6(N6) = 7/3 blends compatibilized with systematically modulated amount of maleated polypropylene(mPP) were investigated. The changes in their mechanical properties as a function of mPP amount were also investigated, and the relation between the microstructural features and the mechanical properties of the blends was described. The most interesting result was that N6 in the blends crystallized completely concurrently with PP at the crystallization temperature of PP when the blends contained more than 1.5 phr of mPP. It could be suggested that this phenomenon was mainly due to the size reduction of N6 dispersion as the added amount of mPP increased. Each maleic anhydride group in mPP reacted with one terminal amine group of N6 to form N6 grafted PP with imide type junction point. The grafted N6 were constrained in their segmental mobility which led to the crystallinity reduction of N6. Due to the concurrent crystallization the crystal structure of N6 became partially γ-form which was known to occur when N6 crystallized under supercooling. The mechanical properties such as tensile modulii and yield strengths showed maxima when 1.5 phr of mPP was added into the blend. The impact strengths of the blends depended appreciably on their morphology. The synergistic effect was shown in the noncompatibilized blend having rod-like N6 domain, whereas it was not observed in the compatibilized blends with sea and island morphology.