Abstract: This paper investigated the physical and chemical performances of four main invisible align thermoplastic materials, including BiolonTM, ErkodurTM, ScheuTM and DR ProformTM. The mechanical and thermal properties of these four materials were analyzed by mechanical measurements and differential scanning calorimetry, while their chemical compositions and optical properties were characterized by FTIR spectroscopy and ultraviolet- visible spectrophotometry. The results indicated that the thicker materials exhibited a higher elasticity modulus and tensile strength when the material thickness was lower than 1.0 mm. Furthermore, the stresses of four materials relaxed with time under a 5 % displacement, and the Scheus stress relaxation ratio showed a lowest value. FTIR analysis confirmed that these four materials were composed of a novel copolyester based on PETG. DSC analysis identified that the four materials were amorphous polymers with a glass transition platform. The four materials exhibited the light transmittance above 80 % within a visible spectrum of 400~760 nm, indicating that these materials had excellent transparent performance for invisible orthodontics.