An analysis is made of the possibility of developing a high-sensitivity ellipsometric method of monitoring the surface temperature of samples in ultrahigh vacuum. The method is based on the temperature dependence of the phase thickness of the layer being studied. Measurements made for ZnTe layers show that the sensitivity coefficients for the ellipsometric angles ψ and Δ are 0.1 and 0.5° respectively per degree temperature. This is more than an order of magnitude higher than the sensitivity of ellipsometric methods of measuring temperature used conventionally.