Abstract: The polypropylenetin (PPSn) nanocomposites were prepared by melt blending PP and Sn. The factors influencing the morphology of PPSn nanocomposites were studied by SEM. The structure of PP crystalline in PPSn composites was measured by WAXD. The processibility, volume resistivity and mechanical properties of PPSn nanocomposites were discussed. The results show that Sn is the nuclearing agents of PP crystallization and can improve notably the processibility of PP. It is found that there exists form crystalline phase structure of PP in PPSn composite. The amount of the form is related to the volume fraction and particle dimension D of Sn. It is also found that the electrically critical volume fractionc of Sn decreases notably with the decrease of D. The complex tensile moduli of PPSn composites increase with the increase of and the decrease of D. The tensile strentgh of PPSn nanocomposites is eleven times as high as that of PP and the izod impact toughness is 3.3 times as high as that of PP.