To develop a new and efficient biocatalytic synthesis method of imidazole-4-acetic acid (IAA) from l-histidine (l-His). l-His was converted to imidazole-4-pyruvic acid (IPA) by an Escherichia coli whole-cell biocatalyst expressing membrane-bound l-amino acid deaminase (ml-AAD) from Proteus vulgaris firstly. The obtained IPA was subsequently decarboxylated to IAA under the action of H2O2. Under optimum conditions, 34.97 mM IAA can be produced from 50 mM l-His, with a yield of 69.9%. Compared to the traditional chemical synthesis, this biocatalytic method for IAA production is not only environmentally friendly, but also more cost effective, thus being promising for industrial IAA production.