Ind2Y(μ-Et)2A1Et2 and Ind2LnN(i-Pr)2 (Ln = Y, Yb) were used as a single-component catalyst for the polymerization of acrylonitrile (AN) respectively. The regularity of polymerization of AN and stereoregularity of polyacrylonitrile (PAN) were also studied in both cases. Both catalysts can produce PAN with molecular weight from I0,000to 30,000. In addition, the catalytic activity and molecular weights were increased by the addition of PhONa.