The effects of the catalyst concentration，the monomer concentration and the poly-merization temperature on the conversion，average molecular weight and microstructure of the polybutadienes obtained have been studied． Results showed that the characteris-tics of this catalyst system are the extremely low requirement of catalyst and the high and rather constant cis一1，4-content of the polymer．The rate of polymerization is，how-ever，too fast and the molecular weight of the polymer too high． Further studies aimed at controlling the polymerization rate and regulating the molecular weight of the poly-mers showed：(1) The rate of polymerization varies greatly with the solvents，the order of which being benzene> toluene > xylene > mesitylene．(2) Addition of phenyl一β-naphthylamine or N，N’-diphenyl-p-phenylene diamine lowers both the rate of polymerisa-tion and the molecular weight of the polymer．(3) The molecular weight of the poly- met can be regulated by controlling the water content in the system．(4) The molecular weight of the polymer can also be regulated by varying the ratio of the two components of a mixed solvent．(5) Addition of small amount of polynuclear hydrocarbons，such as naphthalene or anthracene to the heptane polymerization solution raised the molecular weight of the polymer to a considerable extent．The above results were discussed．