The purpose of this work is to compare the mechanical properties of the different PP/ Filler composites. We considered the effect of treatment of the filler on the adhesion between the filler and the matrix. Modification of polypropylene (PP) with different coated and uncoated fillers is investigated in this paper. Six types of different fillers are used for preparation of filled PP composites. The composite samples were homogenized in a twin screw extruder. The compatibility of PP and fillers focused in this study and modified by using coupling agent. The obtained values of composites were cor- related with mechanical properties.