Physicochemical and thermal properties of L-phenylalanine ammonia-lyase preparation were studied. Thermal gravimetric analysis of physical and chemical phenomena occurring in the enzyme upon heating was conducted. Heating curves were registered. Kinetic parameters of the evaporation process were identified. Stability of the enzyme to freezing was verified. Cryoscopic temperature of a concentrated L-phenylalanine ammonia-lyase sample was identified. Chemical (dehydration, dissociation) and physical transformations accompanied by exothermic and endothermic effects were found to occur during freezing. Results of the thermal gravimetric analysis demonstrated feasibility of freeze-drying of L-phenylalanine ammonia-lyase preparation and allowed for determination of the optimum temperature ranges for thermal treatment and prediction of operational parameters of the drying process.