The invention belongs to the technical field of fire-fighting supplies, and relates to a foam fire extinguishing agent, which is composed of the following components by mass percentage: 1.2% to 3.0% of fluorocarbon surfactant, 12% to 25% of deproteinized solution, and 1.5% of perfluorobetaine ~3.5%, alkyl glycoside 10%~16%, urea 3%~5%, starch 5%~8%, food flavor 0.03%~0.15%, ethylene glycol 10%~20%, xanthan gum 0.1%~ 0.3%, foam stabilizer 0.5%~1.0%, cosolvent 0.8%~1.5%, thickener 0.1%~1.2%, and the balance is water. The composition of the present invention is scientific. Compared with the traditional foam fire extinguishing agent, the present invention has an aromatic smell, lower corrosion rate than the traditional foam agent, can prolong the storage life, has low energy consumption, and produces no three wastes. During production and use It will not pollute the environment, will not cause harm to the human body, and each component is easily biodegradable, with fast cooling speed, no recombustion, stable use, and greatly improved the speed of fire extinguishing.