The invention discloses a high-nodularity nodulizer for nodular cast iron. The nodulizer is prepared from the following components in percentage by weight: 16% of Mg and Si, 3.0% of Re, 2.1% of Ca, 2.0% of Ba, 0.05% of Bi, 0.09% of Ti, 0.3% of Al, 1.0% of rare earth and Fe in balancing amount. The nodulizer prepared according to the invention adopts rare earth made from yttria, gadolinium oxide, holmium oxide and cerium oxide, so that the nodulizer is greatly enhanced in molten iron purification capacity, nodulizing capacity, nodulizing degeneration resistance and graphite distortion resistance, has a little chilling tendency, can refine a matrix structure, can prevent a resulfurization phenomenon, has high boiling point, can inhibit interference of anti-nodulizing elements, can improve the impact toughness of the nodular cast iron, can also improve the nodularity and the quality of a casting and has the characteristics of energy saving and pollution prevention; the nodulizer can effectively inhibit a nodulizing degeneration phenomenon of the nodular cast iron and meanwhile can accurately control the nodulizing reaction time; and owing to a synergistic effect of the added elements, the strength, hardness and heat resistance of the alloy can be effectively improved, and the nodularity can be greatly improved.