The invention discloses fatigue-resistance high-strength steel with a nanometer precipitated phase and a preparation method thereof and belongs to the technical field of metal material machining. A steel type has bainite, ferrite and retained-austenite multi-phase organization. Through a reasonable technique, the sizes of grains of a material are controlled to be below 5 [mu]m, the steel is ultra-fine grain steel, and a great number of dispersedly-distributed nanoscale ball-shaped V (C,N) and Ti (C,N) precipitated phases exist in the organization, wherein the average size of the precipitated phases is lower than 50 nm. The material has good strength and elongation performance and excellent fatigue resistance performance, the tensile strength is more than 1100 MPa, the product of strength and elongation is more than 30 GPa.%, and fatigue limit is more than 850 MPa. The fatigue-resistance high-strength steel with the nanometer precipitated phase and the preparation method thereof can be widely suitable for fields such as automobile structure parts, engineering machinery parts and building structural materials.