A study of ethylene copolymerization with butene-1 using the-MgCl2 supported catalysts of alkoxyl titanium chloride has been- proposed. The main interest of the study was related to the effects of number of butoxyl group on the catalytic behavior and the incorporation of comonomer to the main chain of the polymer. Results show that catalytic activity as well as titanium content in the catalysts decreased when the number of butoxyl group in the catalysts increased. Therefore

it could be considered that butoxyl titanium chloride fixedon the sur-face of MgCl2 mainly through chloride bridge

only in defectof chloride they combined through unstable oxygen bridge. The influence ofbutene-1 concentration on the comonomer incorporation and the various properties ofthe copolymer obtained were also observed. The comonomer sequence distributions were measured by 13C-NMR. It could be couclused that the butene-1 units in copolymer occur principally as isolated branches.