A polymeric quenchant. The polymeric quenchant comprises an inorganic nanoparticle, a water-soluble polymer, and water, wherein a weight ratio of the inorganic nanoparticle, water-soluble polymer and water is about 0.05-5:1-5:100. The cooling rate of steel during a quenching process can be adjusted by regulating the components and ratios of the adjusted by regulating the components and ratios of the polymeric quenchant to achieve desirable steel properties.