The invention relates to a preparation method of a porous slurry green body, belonging to the technical field of ceramic and refractory materials. The method comprises five steps of: foam preparation, slurry blending, foam and slurry mixing, green body pouring and green body maintenance. The invention specifically comprises the following steps of: prefabricating bubbles in advance under the action of compressed air through a foaming device by adopting a physical foaming agent so as to provide fine, uniform and stable bubbles; and mixing high-alumina cement, Suzhou clay, pyrophyllite, lime and calcium carbonate according to a required proportion and then adding water to prepare a prefabricated slurry, wherein in the slurry, the high-alumina cement is used as one of ingredients to provide aluminum oxide and calcium oxide, and meanwhile, the characteristics of fast-solidification and fast-hardening of the high-alumina cement are adopted to accelerate the solidification and the hardening of pouring a green pouring body so as to ensure that on one hand, the bubbles are fixed as soon as possible to reduce bubble loss, and on the other hand, the green body is enhanced to reduce the deformation of the green body. The invention can easily prepare a green body with a drying density of 0.34-0.45kg / m<3>, and the compression strength of a corresponding drying green body is 0.15-0.50MPa.