Different　surface　areas　of　alpha-Fe2O3　nanocrystals　have　been　achieved　by　annealing　at　different　temperatures.　Obtained　samples　were　characterized　by　X-ray　diffraction,　Brunauer-Emmett-Teller　technique,　and　transmission　electron　microscopy.　The　surface　areas　of　alpha-Fe2O3　nanocrystals　changed　from　136.5　m(2)/g　to　2.1　m(2)/g　with　the　increase　of　annealing　temperature　from　280　degrees　C　to　700　degrees　C.　alpha-Fe2O3　nanocrystal　catalytic　activity　on　the　decomposition　of　ammonium　perchlorate　(AP)　was　characterized　through　thermogravimetric　analysis.　The　decomposition　rate　of　AP　with　the　addition　of　alpha-Fe2O3　nanocrystals　was　surface　area　relative.　The　136.5　m(2)/g　alpha-Fe2O3　nanocrystal　exhibited　the　best　catalytic　activity,　which　lowered　the　high-temperature　peak　temperature　of　AP　by　60.8　degrees　C.