The novel catalysts of TiCl4-CH3COCH2COCH3-Co(acac)2 supported on SiO2-MgCl2 carrier (Ti-Co complex catalyst) were prepared by reaction procedure．The polyethylene with various branching chains was synthesized by using these Ti-Co complex catalysts．The effects of the kinds of AlR3

polymerization temperation and the constituent of catalysts on the polymerization activity and the product properties were investigated．The polymerized products have analyzed by using IR and 13C-NMR spectroscopies．The results of 13C-NMR studies suggested that the polyethylene products contained n-butyl branches

pentyl branches and long branching chains(n≥6)．The polymerization mechanism was discussed also．Experimental results showed that the Ti-Co complex catalyst with Et2AlCl as cocatalyst exhibited high catalytic activity and excellent properties of oligomerization and in situ copolymerization for ethylene．