Environment-friendly fire extinguishing agent and preparation method

The invention discloses an environment-friendly fire extinguishing agent and a preparation method. The environment-friendly fire extinguishing agent is prepared from the following components in percentage by mass: 0 to 5 percent of trifluoromethane, 30 to 81 percent of heptafluoropropane, 15 to 56 percent of pentafluoroethane, 2 to 15 percent of auxiliary agent and 2 to 12 percent of inert gas, wherein the auxiliary agent is a mixture consisting of 1 to 14.8 percent of at least one of trichloromethane, cis-1-chloro-3, 3, 3-trifluoropropene and trans-1-chloro-3, 3, 3-trifluoropropene, 0.002 to2 percent of at least one of magnesium hydroxide and magnesium oxide, and 0.1 to 1 percent of sodium bicarbonate. The production cost is reduced, the saturated vapor pressure of the system is improved, and the additive is added to generate a positive synergistic fire extinguishing effect with other fire extinguishing agents in the fire extinguishing process so that the fire extinguishing efficiency of the fire extinguishi