The invention discloses high-strength and toughness non-quenched and tempered steel and a preparation method thereof, and belongs to the technical field of structural alloy steel. The N content is increased, Mn, Cr and V are reasonably added, and the V/N mass ratio is accurately controlled, so that the problem of incapability of combining strength, toughness and use cost of non-quenched and tempered steel in the prior art are solved. The high-strength and toughness non-quenched and tempered steel is prepared from the following components according to mass percent: 0.23 to 0.27% of C, 0.22 to 0.35% of Si, 1.81 to 1.90% of Mn, 0.50 to 0.55% of Cr, 0.045 to 0.06% of S, less than or equal to 0.02% of P, 0.11 to 0.14% of V, 0.025 to 0.040% of N and the balance of Fe and inevitable impurities. The tensile strength of the high-strength and toughness non-quenched and tempered steel is greater than or equal to 950 MPa, and the Charpy impact work KU2 (20 DEG C) is greater than or equal to 55 J.The preparation method of the high-strength and toughness non-quenched and tempered steel comprises the steps of smelting, forging and cooling after forging. The high-strength and toughness non-quenched and tempered steel can be used for automobile safety parts.