Abstract: A microwave heat treatment method for granulated blast furnace slag is provided, which includes the following steps: subjecting the granulated blast furnace slag to microwave heat treatment at a frequency of 900-930 MHz and then cooling the slag. Microwave rapid heating is utilized to remove the moisture in the granulated blast furnace slag, stress is generated inside the granulated blast furnace slag particles to promote the formation of cracks or the decomposition of the granulated slag particles into small particles. After the microwave reaches a certain power, the microwave is turned off, an air blower is turned on, and thermal stress is generated inside the granulated blast furnace slag particles, so that the particles are further promoted to generate cracks or fragmentation; and then the desired fine powder can be obtained by ball milling the granulated blast furnace slag after microwave heat treatment for a short time.