This study was carried out to investigate the flora of estuary regions, Namdaecheon, Jusucheon, and Maeupcheon, placed in the east coast of Gangwon-do. The vascular plants were summarized as 441taxa, including 90 families, 277 genera, 388 species, 2 subspecies, 35 varieties, and 6 forms. Number of species in each investigated region was 271taxa of Namdaecheon, 247taxa of Jusucheon, and 285taxa of Maeupcheon, respectively. Among the investigated 441taxa, 7 Korean endemic, 5 rare plants and 37 specially designated plants by Ministry of Environment were also included. Aquatic and hydrophyte plants were collected 41taxa, and the thinophyte and halophyte plants were investigated 22taxa. The naturalized plants were 59taxa, and the percent of naturalized plant species was estimated as 13.3%. Based on the floristic composition, Maeupcheon was estimated as well conserved estuary region among the investigated 3 rivers.