The invention relates to a semi-steel roll and a preparation method thereof, belonging to the technical field of steel rolling. The semi-steel roll contains the following chemical components according to the mass percent: 1.65-1.90 of C, 0.80-1.15 of Cr, 0.35-0.65 of Si, 0.60-1.00 of Mn, 0.30-0.60 of Mo, 0.20-0.80 of Ni, 0.05-0.10 of K, 0.05-0.10 of Na, 0.05-0.15 of Ti, 0.05-0.15 of Nb, 0.08-0.15 of Y, 0.03-0.08 of Mg, 0.02-0.04 of Zn, 0.06-1.00 of Al, less than 0.04 of P, less than 0.03 of S, and the balance of Fe. The semi-steel roll has reasonable chemical component, prolonged service life, the hardness of 55-58 HS and the tensile strength of 900-950 MPa and the impact toughness of 10-12 J/cm2; the invention can save the nickel resource, reduce the cost, simplify the heat treatment, shorten the production period, improve the heat treatment efficiency, save the energy, thin the solidified organization, improve the forms and the distribution uniformity of carbides and inhibit the aliquation of alloy elements;.