The preparation of quantum dot thin films and the accurate measurement of optical constants are particularly important for promoting the development of quantum dot applications in the optoelectronic fields. At present， the optical constant characterization technology for MoTe₂ single crystal thin films prepared by mechanical exfoliation and chemical vapor deposition methods is 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 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 with two sizes were studied by B-spline model and Tauc-Lorentz model using spectroscopic ellipsometry. The results demonstrate that 2H-MoTe₂ quantum dots with two sizes have similar refractive indices， extinction coefficients and a wider spectral absorption range from the visible to near-infrared band. And compared with MoTe₂ bulk material， 2H-MoTe₂ quantum dots have a lower dielectric constant.