Abstract: The high-temperature copper slag is usually cooled by water quenching in the pyrometallurgical process of copper, resulting in the waste of a large amount of high-quality waste heat resources. This study proposed a bottom-blowing air quenching granulation method, in which the gas jet was sprayed from the bottom to impact the melt stream to a liquid film and further break it into droplets. Then, the airflow cooled the liquid droplets and solidified them into particles. The airflow absorbed the heat of the melt and entered the waste heat boiler to realize the waste heat recovery. Experimental platforms of bottom-blowing air-quenching were designed and constructed. Side-blowing and bottom-blowing air quenching experiments were conducted by using liquid wax. Results show that the bottom-blowing air quenching can break the liquid wax into droplets under the conditions of low pressure and low blowing rate, and the granulation process is stable, which is beneficial for extending to industrial applications. A mathematical model of bottom-blowing air quenching multiphase flow was constructed, and the simulations were in good agreement with experimental data. Air quenching process of copper slag was simulated, and the effects of gas flow rate, ratio of melt outlet and gas outlet diameter were analyzed. Results show that it is hard to form a stable liquid film when the gas flow rate is too small, the melt outlet will be blocked when the flow rate is too large, and the melt can form into a liquid film and then break the film into liquid droplets when the flow rate is 100 m/s. Reducing the diameter ratio can quench the melt into smaller, more uniform droplets. Although the film could be formed when the diameter ratio is large, the film will form larger diameter clumps because of the lack of airflow.