Using a fiber-based compact source of entangled photon pairs, we build a single-mode-fiber-coupled scheme for quantum ellipsometry, and measure the ellipsometric parameters for a 100-nm-thick silica film on silicon substrate.The signal photons of the photon pairs are reflected by the sample under test.By performing the two-photon coincidence counting measurement for the entangled states after the reflection, we obtain the ellipsometric parameters of the sample.When the wavelength and incident angle of the photons sent to the sample are 1558.17 nm and 30 °, the measured ellipsometric parameters (ψ,Δ)are 40.23 ° and 173.10 °, with standard deviations 0.046 ° and 0.403 °, respectively.The relative standard deviation of the meausred results is less than 1％, and the results agree well with theoretical predictions.