5-Aminotetrazole was synthesized from dicyandiamide and sodium azide in water with zinc bromide as catalyst. The effects of reactant molar ratio, catalyst consumption, temperature and reaction time on the reaction were discussed. The experimental results show that when the molar ratio of sodium azide to dicyandiamide is 1∶1.6 and catalyst consumption of sodium azide to zinc bromide is 1∶0.3, the reaction temperature is 75-85 ℃ and the reaction time is 5.5 h, the yield of 5-aminotetrazole reaches 83.6%. ZnBr_２ is a good catalyst to synthesize 5-aminotetrazole.