Preparation method of N-acetyl-D-glucosamine

The invention relates to a preparation method of N-acetyl-D-glucosamine, which is characterized by comprising the following steps of: reacting D-glucosamine hydrochloride as a raw material in an alkaline substance solution RCH2OX or XH to separate out solid chlorate and generate free D-glucosamine; filtering out the solid chlorate to obtain a free D-glucosamine solution; and directly carrying outacetylization reaction on the free D-glucosamine solution to generate the N-acetyl-D-glucosamine by using acetic anhydride. The preparation method avoids using toxic organic solvents, i.e. expensive tributylamine or triethylamine and the like, has easy operation of the whole process and advanced process and can achieve the yield coefficient by 85-95 percent without pollution basically; the obtained N-acetyl-D-glucosamine has good colour and luster; adopted equipment is most general equipment; adopted auxiliary materials are organic materials which are ordinary and easy to obtain; and in addition, the invention has low