The invention relates to an alloy cast steel roll and a preparation method thereof, and belongs to the technical field of steel rolling. The roll comprises the following chemical components in percentage by mass: 0.70 to 0.85 percent of C, 0.90 to 1.20 percent of Mn, 1.02 to 1.16 percent of Cr, 0.25 to 0.45 percent of Mo, 0.17 to 0.44 percent of Si, 0.03 to 0.08 percent of V, 0.01 to 0.03 percent of N, 0.04 to 0.10 percent of Nb, 0.04 to 0.10 percent of Ti, 0.02 to 0.08 percent of La, 0.02 to 0.08 percent of Ce, 0.03 to 0.08 percent of Al, 0.005 to 0.015 percent of Ca, 0.002 to 0.006 percent of B, 0.003 to 0.015 percent of Te, less than 0.03 percent of S, less than 0.03 percent of P, and the balance of Fe, wherein the sum of the La and the Ce is more than or equal to 0.06 percent and less than or equal to 0.12. The roll has the advantages that the roll has lower production cost; the comprehensive mechanical property, thermal fatigue property and abrasion resistance of the roll are improved, and the service life thereof is prolonged; the tensile strength reaches 1,200 to 1,280 MPa, the elongation rate reaches 15 to 18 percent, the impact ductility reaches 22 to 25 J/cm<2>, and the hardness reaches 45 to 48 HSD; and the operation rate of a rolling mill is improved.