Abstract: The composites of low molecular weight functionalized polyisobutene with montmorillonite were prepared as one of blend compatibilizers for improving the mechanical properties of polypropylene. The influences of active agent and blend temperature on the mechanical properties of the polyisobutene-montmorillonite/polypropylene composites were investigated. The SEM and TEM images of montmorillonite in the polypropylene matrix were observed. The results reveal that the montmorillonite disperses well in the polypropylene matrix because of the effect of the functionalized polyisobutene and the active agent. When 4wt% montmorillonite and 1wt% (of montmorillonite) active agent are used in the composites，the properties of polyisobutene-montmorillonite/polypropylene composite，such as modulus of 2280MPa，impact strength of 63J/m and recovery ratio of 0.5%，are obviously bet ter than those of the pure polypropylene. The size of montmorillonite dispersed in the polypropylene matrix is about 1μm.