Inonotus obliquus or chaga birch mushroom has a fairly wide range of applications in the cosmetic, food and pharmaceutical industries due to the wide range of biologically active substances it contains. The analysis of foreign and domestic studies testifies to the ongoing research in the field of extraction of valuable components from chaga, however, issues of intensification of processes and the development of new methods of extraction remain topical. One of these methods is the water-vacuum extraction of chaga, which consists in alternating the stages of the process at atmospheric and reduced pressure. The aim of the study is to determine the optimal time parameters of the individual stages of the water-vacuum extraction of chaga to optimize the operating parameters of the process. The object of the study was chaga collected in forest plantations in central Russia in the spring season, and crushed to particles ranging in size from 0.1 to 1.2 mm. The experiments were carried out on a laboratory version of a vacuum extraction unit, which allows for the classical infusion and extraction of chaga at various variations in the pressure of the medium. Studies have shown that preliminary evacuation of dry raw materials and the introduction of a rarefied medium into the process of water extraction of chaga makes it possible to intensify the extraction process and has a positive effect on the yield and activity of extractive substances. It has been established that the preliminary evacuation of crushed chaga makes it possible to increase the efficiency of subsequent extraction and to increase the yield of valuable components by 15-18%. The optimal time for this stage was 5 minutes. The effective duration of the infusion step at atmospheric pressure was 30 minutes, and the subsequent evacuation is expediently carried out for 10 minutes. Based on the results of the presented work, the optimal scheme for carrying out the process of water-vacuum extraction of chaga was determined.