Combination of Ni2O3 and solid acid with Bronsted acid sites and Lewis acid sites (such as HZSM-5 and H-beta) could dramatically improve fire retardancy of polyolefin, including polypropylene and linear low-density polyethylene. This is mainly attributed to the formation of a large amount of residual char from degradation products of polyolefin in the intermediate stage of combustion. Thus, the amount of flammable components diffusing into the flame zone was small. The investigation on the combined effect of solid acid and Ni2O3 showed that the presence of cationic reactive intermediates, mainly originating from Bronsted acid sites on the solid acid, strongly promoted carbon deposition of the degradation products. As a general method for improving fire retardancy of polyolefin, optimizing combination of metal catalyst and solid acid will further promote efficiency of fire retardancy.