In this research the effect of both calcium carbonate nanoparticles and PP-g-MA ones on impact strength and Young’s modulus of Polypropylene (PP) are investigated experimentally. Two kinds of CaCO3 nanoparticles (monolayer-coated and uncoated) are used to investigate the effect of surface treatment of nanoparticles on the mechanical properties of these composites. All samples are mixed in a co-rotating twin screw extruder and are formed into standard tensile and impact bars using the injection molding method. The effect of surface modification of nanoparticles and presence of PP-g-MA on the dispersion of calcium carbonate nanoparticles in polypropylene matrix are studied by field emission scanning electron microscopy (FESEM). The results show a good agreement between the TGA analysis and the related theory. The results also show that surface modification of calcium carbonate nanoparticles and also the PP-g-MA are affective in improving the distribution and dispersion of nanoparticles in the PP matrix. Increasing of the calcium carbonate nanoparticles improves both the impact strength and the Young's modulus of polypropylene. The more the PP-g-MA is added to PP matrix the more the impact strength of the samples increases and the less their Young's modulus decreases.