The invention provides a deacetylase, a coding gene and an application thereof. The deacetylase of the present invention is as follows a) or b) or c): a) a protein encoded by an amino acid sequence asshown in SEQ ID NO. 2; b) a fusion protein obtained by connecting a tag on the N-terminal and/or C-terminal of the protein as shown in SEQ ID NO. 2; c) a protein having the same function obtained bysubstitution and/or deletion and/or addition of one or several amino acid residues of the amino acid sequence as shown in SEQ ID NO. 2. The invention further relates to the use of such proteins in thepreparation of glucosamine. The invention also relates to biological materials related to the protein. The deacetylase of the invention can efficiently catalyze deacetylation reaction of the N-acetylglucosamine monosaccharide and can be applied to the industrial preparation of glucosamine. The reaction conditions are mild, the conversion rate is high, no pollutants are generated, and the acetylglucosamine monosaccharide has a good industrial application prospect.