A novel process of preparing 1H-tetrazole acetic acid was reported in this paper. Firstly, 5-amino tetrazole was synthesized in 85% yield from hydrazine hydrate and cyanamide. The second step was deamination reaction (the yield was 95%). The last step was nucleophilic substitution. Under basic condition, 1H-tetrazole acetic acid was produced by 1H-tetrazole and chloroacetic acid in 81.7% yield. Water was used as the reaction medium in the above steps. The total yield of 1H-tetrazole acetic acid was higher than 65%. In this paper, the most important work focused on the optimization of nucleophilic substitution. The better conditions for this substitution: reaction temperature 100 ℃, n(1H-tetrazole):n(ClCH2COOH):n(NaHCO3)＝1:1:2.2, the reaction time 20 h.