The invention discloses porous high-entropy alloy and a preparation method thereof and belongs to the field of porous foam metal. The preparation method of the porous high-entropy alloy specifically comprises the steps that high-entropy alloy powder and screened pore-forming agents are mixed proportionally according to the requirements for the porosity and the pore size, and the high-entropy alloy powder and the screened pore-forming agents are sintered through spark plasma sintering (SPS) directly after being uniformly mixed by a blender mixer; after sintering is completed, a sintered sample is put into deionized water to be subjected to ultrasonic cleaning, and particles of the pore-forming agents are removed by using the characteristic that the pore-forming agents are soluble in water; and finally the porous high-entropy alloy is obtained. The preparation method is simple in process, particularly, the preparation time is shortened greatly through the SPS method, and the efficiency is improved. The prepared porous high-entropy alloy has the characteristics of being high in porosity, uniform in pore size distribution, controllable in porosity and pore size and the like and has potential application prospects in the fields of biology, petroleum, metallurgy, chemical industry and the like.