A grouD of polypropylene (PP)／barium sulfate (BaSO4) composites with different polymer-filler interfacial interaction were prepared by treating the fillers with coupling agents or incorporating functionalized PP (PP-g-MAH)．The effect of interfacial modification on the rheological and crystalline behavior of the composites was investigated．It is shown that the interfacial adhesion between the filler and matrix was increased when the fillers were treated with silane or tlle PP-g-MAH was added into the composites．Under such circumstances,the mobility of the PP chains decreased,leading to high shear viscosity,shear stress and melt elasticity．On the other hand,the improved polymer-filler compatibility contributed to the increase of the heterogeneous nucleating activity of the filler on the PP．A model of“effective occupied volume” was employed to illustrate the effect interracial interaction and a parameter was introduced to evaluate the interfacial interaction quantitatively．