The invention discloses a fire extinguishing device for expanded polystyrene, and belongs to the technical field of fire fighting equipment. The fire extinguishing device comprises an induction mechanism and a fire extinguishing mechanism, wherein the induction mechanism comprises a sliding plate, a sliding cavity and a platform with an open top and a hollow interior. The sliding plate is vertically and slidably connected in the platform. The fire extinguishing mechanism comprises a support frame, a motor, a fire extinguishing cover and a pulley rotatably connected to the top of the support frame. The pulley is wound with a rope, and one end of the rope is fixedly connected to the top of the fire extinguishing cover. The fire extinguishing cover is used for covering the expanded polystyrene, the motor comprises a driving shaft, the driving shaft is fixedly connected with the other end of the rope, and a conducting loop is formed among the motor, a first carbon rod pole and a second carbon rod pole. The fire extinguishing cover can cover the expanded polystyrene on fire and can extinguish the fire quickly.