Abstract: A method for preparing an MOFs flame retardant modified by layer-by-layer self-assembly of an intumescent flame retardant is provided. The method mainly includes the steps of preparing MOFs, a positive electrolyte solution, and a negative electrolyte solution; dispersing the MOFs in the negative electrolyte solution; dispersing an obtained mixture in the positive electrolyte solution; obtaining a first double-molecule self-assembled layer on surfaces of the MOFs; and repeating the above operations for several times to obtain an MOFs flame retardant modified by intumescent self-assembled layers. The modified MOFs flame retardant of the present disclosure has excellent flame retardancy, flame retardant synergism, and dispersibility, and the defects of poor dispersibility and low flame retardant efficiency of MOFs flame retardants are overcome. A great application prospect is achieved.