We propose a precise ellipsometric method for the investigation of coherent light with a small ellipticity. The main feature of this method is the use of compensators with phase delays providing the maximum accuracy of measurements for the selected range of ellipticities and taking into account the interference of multiple reflections of coherent light. The relative error of the ellipticity measurement in the range of 7.5 × 10 −4 ÷ 4.5 × 10 −3 does not exceed 2%.