The invention discloses a preparation method of glucosamine sulfate, relating to a compound containing aminosugar. The preparation method of glucosamine sulfate has the advantages that a great deal of sulfate precipitation by-product is avoided being generated and a great deal of organic solvent is avoided being used, the operation is in complete aqueous phase, the production processes are safe, the sulfuric acid removed by the membrane method can be recovered and used, the production cost is reduced, exhaust and waste residue are not produced, the prepared product does not contain sodium, potassium or chlorine, the purity of the product reaches over 95 percent, and the glucosamine sulfate can be used to treat osteoarthritis without usage taboo. The preparation method is characterized in that chitin is adopted as the raw material, and a degradation agent of concentrated sulfuric acid is used to cause the chitin to generate degradation reaction; diluted sulfuric acid is used as a deacetylation agent to cause the degraded chitin to generate deacetylation reaction; the chitin which is not reacted after the deacetylation reaction is filtered, and the unreacted sulfuric acid is removed by the membrane method; and the solution, in which the unreacted sulfuric acid is removed, is decolorized, concentrated and dried, and glucosamine sulfate is obtained.