In the last few years the use of polypropylene has shown the highest growth rate among all polymers due to its versatility and possibility to vary its mechanical properties by compounding and blending techniques. Mechanical and rheological properties of highly filled polymer composites are dominated by interfacial interaction. In the present work, rheological and mechanical properties of polypropylene filled with barium sulfate were studied. Filler content, interfacial interaction between filler and matrix, and screw speed are the parameters which were investigated. Interfacial interaction between filler and PP was improved through three methods; a) using MA-g-PP as compatibilizer b) coating of the filler with stearic acid and c) using coated filler and MA-g-PP instantaneously. The results showed that coating of the filler leads to improve impact strength of the compound in whole range of the filler content (30 to 60 % wt.), which can be arrtributed to improvement of interfacial interaction between filler and matrix. Whereas, increasing of the MA-g-PP concentration in the compound leads to decrease the impact strength. It seems that MA-g-PP makes a thicker interface rather than stearic acid coated filler. SEM micrographs of the compounds, compatibilized with MA-g-PP, clearly showed that the surface of the filler particles covered with thick layer of polypropylene which reduces dissipation mechanism in fracture, which is contrary to compounds with coated filler. Linear viscoelastic data showed a nonterminal region for storage modulus in low frequency, which attributed to formation of a three dimensional network of the filler particles in high concentration. In the other hand, existence of MA-g-PP made the storage modulus increase in nonterminal region which indicated formation of the network with high stability. It was concluded that the amount of stearic acid and MA-g-PP should be optimized to produce a high performance highly filled PP with barium sulfate.