The invention relates to a chemical fire retardant for controlling spontaneous combustion of lignite of a power plant. At present, no chemical fire retardant for controlling spontaneous combustion of lignite of the power plant, which is especially suitable for spontaneous combustion of lignite and good in fire retardance effect, and accords with the requirement of environment friendliness of the power plant, exists. The chemical fire retardant is characterized by comprising 0.5-1 percent by weight of component A, 0.1-0.5 percent by weight of component B, 0.1-0.5 percent by weight of component C and the balance of water, wherein the component A is polymer absorbent resin, the component B is a surfactant, the component C is a film forming agent, and the pH value of the chemical fire retardant is 5.0-7.0. The chemical fire retardant is especially suitable for spontaneous combustion of lignite, and good in fire retardance effect, and accords with the requirement of environment friendliness of the power plant.