Sulfation of birch wood xylan by chlorosulfonic acid in 1,4-dioxane was studied for the first time. It has been found, that sulfation of xylan at a temperature of 20 °C for 5–6 hours makes it possible to obtain xylan sulfates with a degree of sulfur substitution 1.2. The optimum conditions of the reaction were found which allow to carry out the sulfation of xylan in milder conditions, as compared to known methods.