The innovative and environmentally friendly methodologies for comprehensively enhancing the performances of high-strength steels without damage to plasticity, toughness and heat/corrosion/fatigue resistance are being developed. In recent years, nanoparticles elevate the field of high-strength steel. It is proposed that nanoparticles have the potential to replace conventional semi-coherent intermetallic compounds, carbides and alloying to optimize the steel. The fabrication process is simplified and the cost is lower compared with the traditional methods. Considerable research effort has been directed towards high-performance cast steels reinforced with nanoparticles due to potential application in major engineering. Nanoparticles are found to be capable of notably optimizing the nucleation behavior and precipitate process. The prominently optimized microstructure configuration and performances of cast steel can be acquired synchronously. In this review, the lattice matching and valence electron criterion between diverse nanoparticles and steel are summarized, and the existing various preparation methods are compared and analyzed. At present, there are four main methods to introduce nanoparticles into steel: extal nanoparticle method, intal nanoparticle method, in-situ reaction method, and additive manufacturing method. These four methods have their own advantages and limitations, respectively. In this review, the synthesis, selection principle and strengthening mechanism of nanoparticles in cast steels for the above four methods are discussed in detail. Moreover, the main preparation methods and microstructure manipulation mechanism of the steel reinforced with different nanoparticles have been systematically expatiated. Finally, the development and future potential research directions of the application of nanoparticles in cast steel are prospected.