Polypropylene samples prepared with supported Ziegler-Natta catalysts were fractionated with temperature rising elution fractionation(TREF) technique and the tacticity distributions were obtained. It is found that the polypropylene sample has a broad tacticity distribution when there exists no electron donor in the catalyst. the mutiple maximal wi(%)/At values indicates the presence of plural active sites in the catalysts. Experimental results show that both external and internal electron donors can narrow the tacticity distribution of PP.When external and internal electron donors are present in the catalysts, the obtained PP has the narrowest tacticity distribution.