Increasing the toughness of polypropylene with an elastomer has been suggested by researchers in the field of polymer science and technology. Now due to the decrease of mechanical properties by adding elastomer, adding a third stiff component seems to be necessary to prevent the decrease of mechanical properties. Therefore, in this project, the factors affecting the morphology of the polypropylene/poly(butylene-terephthalate)/ styrene-butadiene-styrene ternary system and their relationship with the mechanical properties have been studied. In this regard, the effect of the two factors including the composition of compatibilizer (styrene-ethylene-butylene-styrene grafted on maleic anhydride) and the composition of PBT and as the effective factors on the morphology was investigated. It was found that by changing the ratio of to SEBS-g-MA in the constant composition of the blend components (PP/PBT/:70/15/15), the morphology and mechanical properties (modulus, tensile strength, yield stress, elongation at breakpoint) and the impact strength were affected by the presence of this evolution, which reduced Young apos;s modulus from 1263 to 908 (MPa) and increased the impact strength from 3.82 to 10.6 (kJ/m2). Also by increasing the rubber phase from 5 to 30 wt% of the System, the Young apos;s Modulus decreased from 1290 to 823.8 MPa and its impact strength increased due to the presence of core-shell microstructures and independent rubber droplets from 4.49 to 47.9 (kJ/m2). It was also found that by increasing the composition of the PBT composition from 5 to 30 wt%, the rod-like microstructure gradually formed and Young apos;s modulus gradually increased from 1167.5 to 1430 MPa, but still decreased with respect to the matrix phase. This is due to the complex morphology observed and the impact strength decreased from 5.9 to 4.09. Finally, the optimum sample was reported to be 72% wt% PP, 20% wt% PBT, 8% wt% of the total and SEBS-g-MAH with 50.50% lower than pure PP. Keywords : Mechanical properties, Polypropylene (PP), styrene-ethylene-butylene-srtyrene (), Polybutyleneterephthalate (PBT), Ternary polymer blends, Core-shell morphology