Abstract: Based on the results of analytical experiments on the fabrication process of hollow glass microspheres (HGMs) in drop-tower furnace and the test results of intermediate product of different stages, the heat, mass and momentum transfer processes in the transformation from dried-gel particle to HGMs were studied. The transformation process from dried-gel particle to HGMs in drop-tower furnace was characterized as heating, encapsulating, foaming, refining, and cooling stage. Furthermore, the heating and encapsulating rate of dried-gel particle, the decomposition temperature and gas-forming ratio of blowing agent, refining time of liquid HGMs, and cooling rate of liquid HGMs are found to be the key parameters to the quality of HGMs.