The invention discloses an organic/inorganic composite microcapsule fire-extinguishing agent, and belongs to the field of fire-fighting materials. The organic/inorganic composite microcapsule fire-extinguishing agent comprises the following components in percentage by weight: 15 to 25 percent of monoammonium phosphate, 60 to 75 percent of ammonium sulfate, 0.5 to 1.5 percent of urea, 1 to 2.5 percent of potassium chloride, 4 to 9 percent of sodium silicate, 0.1 to 0.5 percent of fatty acid zinc, 0.2 to 0.5 percent of fatty acid magnesium and 1.5 to 2 percent of methyl silicane, wherein the sum of the components is 100 percent. According to the organic/inorganic composite microcapsule fire-extinguishing agent, grain diameters of the components are controlled, and the components are microencapsulated by a special process to prepare the fire-extinguishing agent, so that the fire-extinguishing agent cannot deteriorate after being used for 7 years and is inert at the temperature of less than 60 DEG C, and the standard of a product is applicable to international standard organization (ISO), European norm (EN) 615 and national standard (GB) 4066.2-2004; and the fire-extinguishing agent contains nutrient elements such as N, P, K and B which are required by plants and is absolutely harmless to human and animals, and microbes can be degraded within three days, so the organic/inorganic composite microcapsule fire-extinguishing agent is the most ideal 'reen' fire-extinguishing agent which is environment-friendly and low in cost and does not have carbon emission, is efficient in fire-extinguishing performance, wide in fire-extinguishing range and low in production cost and has high economic and social benefits.