The invention discloses a preparation method of nanometer melamine foamed plastic loading phosphate. The preparation method is characterized by comprising the following steps: taking 120 parts of melamine formaldehyde resin in parts by weight, adjusting PH of the melamine formaldehyde resin to be 9 by a regulator, keeping the temperature to be 40 DEG C, adding 5 to 12 parts by weight of phosphate,3 to 10 parts by weight of nonylphenol polyoxyethylene ether, 3 to 8 parts by weight of para-toluenesulfonic acid, 8 to 15 parts by weight of vulcanized rubber, and 5 to 10 parts by weight of propylene glycol, and performing dispersion for 2 h in a 20 KW ultrasonic condition; and then sequentially adding 8 to 12 parts by weight of a foaming agent, 5 to 12 parts by weight of a surfactant, 5 to 7 parts by weight of an opening agent, and 10 to 15 parts by weight of a curing agent, mixing, uniformly stirring, performing microwave foaming for 2 min with the frequency being 2450 megahertz and powerbeing 2 KW, and then drying for 1 h in a drying oven at 230 DEG C, so as to obtain the nanometer melamine foamed plastic loading phosphate. The preparation method can effectively improve tenacity ofa melamine foamed plastic material, reduce the fragility, and ensure that the material has more stable fire resistance.