As one of a series approaches in using two-component and three-component donor-free Ziegler-Natta catalysts, in this preliminary work, the effects of various preparation and polymerization conditions including catalyst preparation by wet- or dry- grinding, the type of cocatalyst, with or without pretreatment of catalyst by cocatalyst before polymerization, Al/Ti molar ratio and polymerization temperature, etc., on the isospecific nature of active sites of the TiCl3 catalyst were studied through a systematic characterization of the PPs by a combination of GPC, C-13-NMR with TREF method. It was demonstrated that the types of Al-alkyl cocatalysts play the most dominant role in determination of isospecificity of activate sites and its distribution. A plausible mechanism (Scheme 1) regarding the formation of isospecific active sites with different stability in terms of Ti-Al bimetallic complexing depending on the type of cocatalyst had been proposed. Except the catalyst grinding method, other factors eg., pretreatment, temperature, and Al/Ti molar ratio, etc. did not show obvious effects on the isospecific nature of active sites.