A porous material and preparation method thereof is provided. The material includes a material body. The body consists of pore cavities classified according to pore size of material and cavity walls surrounding to form the pore cavities. The lower-level pore cavities are arranged on the cavity walls of the upper-level pore cavities framed by surrounding a three-dimensional space. All the pore cavities are interconnected. The preparation method is: mixing raw powders with pore-forming agent for the smallest-level pore cavities of porous material to formulate slurry； uniformly filling the slurry into polymer material support to form green body and get dried and smashed to obtain mixed grains； uniformly mixing the mixed grains with pore-forming agent for upper-level pore cavities greater than the smallest-level pore cavities of porous material to make compact green body； performing vacuum sintering； performing the conventional follow-up treatment according to the raw materials process of porous material.
