The invention provides a device for recycling and treating the waste heat of high-temperature steel slag. The device comprises a fixed support, a pipeline, water pumps, a steam storage tank, a one-way pressure valve, a water replenishing tank, a well type tank device, heat-exchanging devices and a slag sealing cover, wherein the tank body of the well type tank device is made of heat-resistant concrete, and the heat-exchanging devices are fixedly mounted on the inner sides of the tank body; the heat-exchanging devices comprise steel plate protection frames and bent frames made of steel pipes; the slag sealing cover covers the well type tank device. The invention further provides a method for recycling and treating the waste heat of high-temperature steel slag, the method comprises the following steps: high-temperature liquid slag, crusted slag and half-molten slag with a temperature about 1200-1500 DEG C are poured into the well type tank device, the high-temperature steel slag is pounded by a special machine, the slag sealing cover covers the well type tank device, after heat exchange is performed on the high-temperature slag in the well type tank device and the water running in the heat-exchanging devices, the high-temperature slag is converted into water vapor, the water vapor is transferred to the steam storage tank through the water pumps and then transferred to a user. The device and method for recycling and treating waste heat of high-temperature steel slag have the advantages of energy conservation, high efficiency, security and reliability, environmental protection, zero emission and the like.