The invention belongs to the technical field of high polymer materials. The modified melamine foamed plastic is prepared from the following raw materials in parts by weight: 25 to 65 parts of melamine, 20 to 45 parts of paraformaldehyde, 15 to 40 parts of water, 0.1 to 1 part of sodium hydroxide, 1 to 8 parts of a stabilizer, 2 to 5 parts of a flame retardant and 3 to 20 parts of a modifier. The melamine foamed plastic prepared by the invention is low in formaldehyde content, high in oxygen index and low in combustion heat value, has better flame retardance and environmental protection performance, and meanwhile, is low in cost and wide in market application prospect.