The invention relates to an alloy for a cutter ring of a disk type hobbing cutter, which comprises the following components in percentage by mass: 0.4-0.46% of C, 0.45-1.0% of Si, 0.48-0.74% of Mn, 1.3-5.4% of Cr, 0.4-1.4% of Mo, 0.86-1.33% of V, 0.06-0.54% of Nb, 0-0.05% of Al, 0-3% of Ni, no more than 0.009% of S, no more than 0.03% of P and the balance of Fe. The preparation method comprises the following steps: performing vacuum induction smelting on the raw materials, casting, forging, performing spheroidal annealing, performing gas carburization, performing vacuum quenching, and performing double tempering. The carburized layer of the prepared cutter ring of a disk type hobbing cutter is 1mm thick, the surface hardness of the carburized layer can be up to 60-63HRC, the internal average hardness is higher than 55HRC, and the impact toughness aku is up to 15-22J / cm<2>; and the shield cutter ring is high in hardness and favorable in toughness.