In this work we discussed the process of lyophilisation. The nature of process allows the removal of water from products, without them being exposed to higher temperatures that could potentially destroy their properties. It is one of the fundamental processes in the processing of pharmaceutical products and foods, and has an enormous impact on storage time and stability of said products. Within the process we focused on part of the process that is called secondary drying stage. Secondary drying stage is characterized by removal of water bound on the dried product with desorption. Theoretical principles of the process are presented to help us understand the process. A model of secondary drying stage of lyophilisation process is created, which enables the analysis of the influence of key parameters on dynamics of the process. The comparison of calculated values with the experimental values from literature has shown promising results.