Land surface water cover (LSWC) PALSAR is obtained in this study by setting an inundated threshold using the interval estimation and Otsu’s methods. By comparing the HH value (dB) obtained using these two methods along with image interpretation, the HH value with (μ + 3σ) is considered the most reasonable inundation threshold. After masking with μ + 3σ, LSWC of PALSAR was mapped and an exponential function with index NDFI (normalized difference frequent index) and NDPI (normalized difference polarization index) of AMSR-E corresponding to PALSAR LSWC was derived by applying the least squares method. It was found that the exponential regression curve could precisely represent the scatter points and the determination coefficient reached more than 0.8. Both NDFI and NDPI have a good fitting result with PALSAR LSWC. Spatial correspondence is finally discussed between AMER-E NDFI/NDPI LSWC and PALSAR LSWC. A high correspondence is shown between each map. It was also found that PALSAR slightly underestimated the inundated area because of the different PALSAR and AMSR-E mechanisms. Using more precise AMSR-E calibration by PALSAR, the availability and potential of AMSR-E LSWC for large scale flooding detection is indicated.