The ammonia decomposition reaction has been of increasing interest as a means of treating ammonia in flue gas in the presence of precious metal catalyst. Various catalysts, Pt-Rh/Al2O3, Pt-Rh/TiO2, Pt-Rh/ZrO2, Pt-Pd/Al2O3, Pd-Rh/Al2O3, Pd-Rh/TiO2, Pd-Rh/ZrO2, Pt-Pd-Rh/Al2O3, Pd/Ga-Al2O3, Rh/Ga-Al2O3, and Ru/Ga-Al2O3, were synthesized by using excess wet impregnation method. Using a homemade 1/4" reactor at 10,000~50,000 hr-1 of space velocity in the presence of precious metal catalyst ammonia decomposition reactions were carried out to investigate the catalyst activity. The inlet ammonia concentration was maintained at 2,000 ppm, with an air balance. Both T50 and T90, defined as the temperatures where 50% and 90% of ammonia, respectively, are converted, decreased significantly when alumina-supported catalysts were applied. In terms of catalytic performance on the ammonia conversion in the presence of hydrogen sulfide, Pt-Rh/Al2O3 catalyst showed no effect on the poisoning caused by hydrogen sulfide. These results indicate that platinum-rhodium bimetallic catalyst is a useful catalyst for ammonia decomposition.