The preparation of quantum dot thin films and the accurate measurement of optical constants are particularly important for the development and application of quantum dot devices in optoelectronic fields. At present， the optical constants of MoTe₂ single-crystal films prepared by mechanical exfoliation and chemical vapor deposition are relatively mature. However， the optical constants of 2H-MoTe₂ quantum dot films are rarely reported.In this work， 2H-MoTe₂ quantum dots were prepared by ultrasonic assisted liquid phase exfoliation， and of 2H-MoTe₂ quantum dots with two sizes were acquired via adjusting the type of solvent and the order of ultrasonic process. The optical constants such as refractive index， extinction coefficient and dielectric constant of quantum dot films of two sizes were studied by B-spline model and Tauc-Lorentz model using ellipsometry. The results demonstrate that the 2H-MoTe₂ quantum dots with two sizes have similar refractive index， extinction coefficient and a wider spectral absorption in the visible to near infrared band. And compared with MoTe₂ bulk material， 2H-MoTe， quantom dots have a lower dielectric constant.