The author investigated the plant sociological studies on the flora of Inchon districts coast area. (It contains also province of Buchun, Kumpo, and Hwasung, the island of Kanghwa.) The scenery of the west coast in Korea is very curious, because the soil in this area contains comapratively large amount of mud and small sand. Some parts of this area is covered with only mud, and the area between the line of high tije and line of low tide is very vast. When a low tide was appearel, there were vast moddel places appeared about 10 km in length. The author could distinguish $varepsilon$ different types of communties in this zone. (1) Suaeda jatonica community (2) Statice japonica community (3) Scirtus triqueier community (4) Zoy_ia community (5) Phragmites community (6) Carex Pumilla community (7) Atriolex subsodata community (8) Rosa rugasa community (1), (2), (3), (4) communities can grow under the high tide. (When the high tide comes they soaked in the sea water.) (1) Suaeda community is the most popular type of the Yellow sea. It is very wonderful scene that the vast area (the length of 10 km) is covered with this Suaeda, and it looks like to be painted with blood. (2) Staice (3) Scirpus (4) Zoysia community is can fully maintain their glorious life in the sea water. It is due to the this plants tolerance of salt. (1), (2), (3), (4) communities are very strong to the tolerance of salt, especially the Suaeda is remarkable. The structure and some sucession I trend of each community were studied in detail and the mutual relations among the communites were also concluded.