Ariake Sea is typical the large-scale closed bay and contains the regional scale tidal flat that account for 40% of Japanese tidal flat total area. A lot of characteristic creatures inhabit Ariake tidal flat and influenced remarkable the environmental functions, topography, grain size water contain, organic substance and sulfide etc. However, the species and the populations of the creature have been decreased in this recent environmental degradation. The aim of this study is to evaluate the habitat environment and recommend the environmental improvement at tidal flat in Ariake Sea. At first we conducted the resource research and the field observation to grasp or in order to grasp and analyze the current tidal flat condition. As a result, the data obtained via cluster analysis was classified into 6 groups and explored the relationship between the environmental characteristic and the habitat.