"The cotton raw material and its components refer to varieties of capillary porous materials, with some special characteristics that distinguishes them from the other known porous materials, such as coal, sand, wood, hemp, flax, etc. Transfer of moisture in the raw cotton and fibrous mass is rather a complicated process, the moisture conductivity here depends on the structure of the material and the nature of the bond of moisture with its pores, etc. The theoretical aspects of the process of moistening cotton of raw cotton are considered in the article, by modelling it with a multi component medium with a structural structure where both internal mass transfer and mass exchange with the external environment are taken into account. This approach allows us to develop a general model for moistening cotton raw, which is close to real situations, thus ensuring the best adequacy of the accepted design scheme"