In this paper, we propose a new method for improving detection of sea ice through use of PALSAR (Phased-Array type L-band SAR) polarimetric data. Unlike traditional methods that are based on backscattering coefficient, our proposed method utilizes scattering entropy to detect sea ice. We tested this method by comparing sea ice area derived from PALSAR fully polarimetric data covering the Sea of Okhotsk acquired in 2009 and 2010 to that derived from reference MODIS (Moderate Resolution Imaging Spectroradiometer) data of the same region. We applied discriminant analysis to samples of sea ice and open water to determine the threshold of PALSAR backscattering coefficient and scattering entropy needed to discriminate sea ice from open water. We found that sea ice area derived from PALSAR data was equivalent to that derived from MODIS data, suggesting that our proposed method was reliable in the detection of sea ice in the Sea of Okhotsk.