In the process of texturing, smooth filaments are formed into crimpy yarns. By combining thermal and mechanical action, thermoplastic fibres acquire a permanent wavy shape. Since textured multifilament yarns, formed from POY PES filaments, produced on machines with high-temperature heaters, are insufficiently studied, this paper analyses the deformation characteristics of yarns produced in industrial conditions using different process parameters (primary heater temperature, yarn speed, yarn stretching, peripheral speed of friction discs). Special attention is paid to the characteristics at the elastic limit, then at the creep limit, yield and breaking of multifilament textured yarns. A method is proposed which can determine the key points of deformation in the process of stretching textured polyester multifilament yarn, as well as the relationship between the values of force and elongation at the limits of elasticity, creep, end of creep zone, yield and break