The invention belongs to the technical field of fire extinguishing materials, particularly relates to an environment-friendly fluoride-free foam extinguishing agent and a preparation method thereof, and solves the problems that a traditional extinguishing agent in the prior art is toxic, not environment-friendly and limited in application range, and a fluorocarbon surfactant, a chelating agent andthe like used in an existing foam extinguishing agent are harmful to the environment. The technical scheme of the invention is as follows: the environment-friendly fluoride-free foam extinguishing agent is formed by mixing a foam concentrate liquid and water according to the volume ratio of 6:94; and the foam concentrate liquid includes the following ingredients: a modified organic silicon surfactant, lauryl sodium sulfate, alkyl glycoside, water-soluble imidazoline, dodecyl dimethyl betaine, dodecanol, polyethylene glycol, xanthan gum, sodium carboxymethylcellulose, ethylene glycol, urea, diethylene glycol monobutyl ether and water. According to the product, a traditional fluorocarbon surfactant is replaced with the modified organic silicon surfactant, so that the product is green and pollution-free, and can be widely applied to fire prevention key units such as oil fields, oil depots, ships, submarines, petrochemical plants, hangars, airports and the like.