The invention belongs to the field of semiconductor testing and measuring, and particularly discloses a polarization reflection measuring system and a structural parameter measuring method, which comprise a spectrograph detector, a focusing lens, a first spectroscope, a second spectroscope, a polarizing film, a reflection type objective lens and a sample table which are coaxially arranged from top to bottom, an illumination light source, a tube mirror and a CCD camera are arranged on one side of the first spectroscope, and illumination light of the illumination light source passes through the first spectroscope, the second spectroscope, the polarizing film, the reflective objective lens and the sample to be detected, then returns along the same path and is converged into the CCD camera through the tube mirror for imaging; and a measuring light source and a collimating lens are arranged on one side of the second spectroscope, and measuring light of the measuring light source passes through the collimating lens, the second spectroscope, the polarizing film, the reflective objective lens and the to-be-measured sample, then returns to the second spectroscope along the same path and is guided into the spectrograph detector by the focusing lens. The imaging light path is added and the position of the polaroid is adjusted so that the measurement area can be accurately represented and the measurement precision can be enhanced.