An experimental study was carried out to investigate the mechanical and rheological properties of particulates filled polypropylene (PP). In order to improve the reinforcement of various fillers (Perlite, CaSO₄ and CaCO₃ for polypropylene, polypropylene was grafted with acrylic acid, in the presence of radical initiator by melt-mixing method in an extruder, The fillers were also treated with acrylic acid. The tensile strength, flexural strength and heat distortion temperature of AA(acrylic acid)-treated sample were higher than untreated on while steady state viscosity of AA-treated sample was much smaller than that of the untreated one except the perlite tilled PP. Die swell ratio was decreased with increasing filler content and die swell ratio of AA-treated sample was smaller than the untreated one.