The authors have made the basic and applied research on the polarimeter for plasma diagnostics. Recently, the authors have proposed an application of multiparameter measurement (magnetic field, B, electron density, n e , electron temperature, T e , and total plasma current, I p ) utilizing polarimeter to future fusion reactors. In this proceedings, the brief review of the polarimeter, the principle of the multiparameter measurement and the progress of the research on the multiparameter measurement are explained. The measurement method that the authors have proposed is suitable for the reactor for the following reasons; multiparameters can be obtained from a small number of diagnostics, the proposed method does not depend on time-history, and far-infrared light utilized by the polarimeter is less sensitive to degradation of of optical components. Taking into account the measuring error, performance assessment of the proposed method was carried. Assuming that the error of Δθ and Δε were 0.1 • and 0.6 • , respectively, the error of reconstructed j φ , n e and T e were 12 %, 8.4 % and 31 %, respectively. This study has shown that the reconstruction error can be decreased by increasing the number of the wavelength of the probing laser and by increasing the number of the viewing chords. For example, By increasing the number of viewing chords to forty-five, the error of j φ , n e and T e were reduced to 4.4 %, 4.4 %, and 17 %, respectively.