In this paper, KHCO3 nanoparticles were uploaded on gamma-Al2O3 to form a new type of powder fire extinguisher comprising KHCO3/gamma-Al2O3 composites through simple impregnation method. The micro morphology, crystallographic form, BET area, and thermal stability of the KHCO3/7-Al2O3 composites were analyzed. Furthermore, the obtained KHCO3/7-Al2O3 composites were used to extinguish a fire and displayed much better extinguishing ability than commercial extinguishers.