The invention belongs to the field of steel material preparation, and particularly relates to an alloy structural steel wire rod for a shaft and a preparation method of the alloy structural steel wirerod. The alloy structural steel wire rod comprises the following elements including, by weight percent, 0.35%-0.44% of C, 0.15%-0.37% of Si, 0.50%-0.80% of Mn, 0.60%-0.90% of Cr, 1.25%-1.65% of Ni, 0.15%-0.25% of Mo, not larger than 0.030% of P/S, not larger than 0.30% of Cu and the balance Al, Fe and inevitable impurities. The preparation method comprises the steps of converter smelting, LF external refining, RH vacuum degassing, bloom continuous casting, intermediate billet rolling, finishing and wire rod rolling. The prepared alloy structural steel wire rod is uniform in structure, wire rod drawing and cold heading machining can be conducted through a softening annealing process, and the technical problems that the structure uniformity of the alloy structural steel wire rod for the shaft is poor, spheroidizing annealing must be adopted before drawing, and the quality stability is poor are solved.