Main goal of this study is to characterize the seasonal variations of radar backscattering according to halophyte species using multi-temporal TerraSAR-X satellite data over Ganghwa tidal flat, then suggest optimum season to define halophyte species. We used SAR backscattering signals from cities to confirm the result of radiometric calibration. Seasonally averaged backscattering coefficients of classes were analyzed by tidal condition. The student t-test was carried out to quantify the separability among different halophyte species (P. australis and S. japonica) and exposed tidal flat based on the averaged backscattering coefficient. Based on t-test, images acquired on late summer in flood condition are suggested to examine the maximized expansion of P. australis and S. japonica. We also investigated the relationship between radar signals and soil adjusted vegetation index (SAVI) to minimize the effect of background tidal flat conditions.