The widespread use of microcrystalline cellulose in various industries and the production of polymer composites from it is due to the growing demand for it as an alternative to non-renewable and scarce fossil materials. Despite the fact that the production of microcrystalline cellulose still has some disadvantages, it has recently attracted increasing interest due to its renewability, non-toxicity, economic value, biodegradability, high mechanical properties, large surface area and biocompatibility. The article shows the possibility of obtaining microcrystalline cellulose from alternative sources of raw materials to expensive business wood — annual plants. Sulfate cooking of annual plant samples (industrial hemp and wheat straw) was performed in a laboratory autoclave under constant conditions: hydromodule 4,5; degree of sulfidity of the cooking solution 18 %; temperature 160 °C. To destroy the outer surface of the fiber shell, increase their active surface and reduce the cost of chemical treatment, the fibrous mass was ground in a semi-industrial disc mill (refining degree 15...85 °C). The water retention capacity of cellulose fibers from industrial hemp bonfires increased by 2,2 times, wheat straw by 2 times, the breaking length respectively by 64 and 52 %, and the penetration by 40 and 34 %. The cellulose samples were hydrolyzed with hydrochloric acid concentration of 73 g/l at 15 °C for 30 minutes and 54,75 g/l at 80 °C for 60 minutes. The degree of polymerization was determined by a viscometric method. The best results were achieved with a refining degree of 85 °C at the campfire of technical hemp — the degree of polymerization is 55, the bulk density is 0,316 g/ml, wheat straw is 95 and 0,239 g/ml, respectively. Thus, the possibility of obtaining microcrystalline cellulose from agricultural waste (bonfires of industrial hemp and wheat straw) with preliminary prehydrolysis refining in a semi-industrial disc mill is shown.