The invention provides a vacuum foaming preparation method of blister steel and belongs to the technical field of a foam metal material. The vacuum foaming preparation method comprises the following steps of: carrying out steel smelting, tackifying a steel melt, generating initial air pores in the steel melt, foaming in vacuum, and cooling a blister steel melt to finally obtain the blister steel with the porosity of 70-85% and the pore diameter of 0.5-5mm. According to the vacuum foaming preparation method disclosed by the invention, SiC is used as a tackifier to carry out tackifying treatment on the steel melt; and a small amount of Cr2N is added into the steel melt tackified by the SiC, and gas is generated by agitating and dispersing the Gr2N and decomposing the Gr2N, so that the initial air pores which are uniformly distributed, great in quantity and fine are generated in the steel melt, and the blister steel is prepared by foaming in the vacuum. The control of the distribution, the quantity, the size, the vacuum degree, the foaming time and the like of the generated initial air pores is carried out so as to control the porosity and the pore structure of the blister steel to prepare the blister steel with the excellent performance in short time. The vacuum foaming preparation method of the blister steel, disclosed by the invention, has the characteristics of high efficiency, simple process, controllable pore structure, stable process and the like, and can realize the industrial production.