Abstract: The species of Alismataceae are chiefly distributed in Lichuau-Enshi-Hefeng-Jianshi, often grow in mountainous swamps and paddy fields mostly with rich humus and acidulous soil (pH value usualy below 7). The species number tends to increase as the altitude increases, yet the distributional amount is the greatest below 800m alt. Although some species have wide distribution, yet most species of this family have very narrow distribution, having fairly strict selection for the habitats, and all these are correlated to the distribution of mountainous swamps and paddy fields.Mainly distributed in subtropical and temperate East Asia, the flora of Alismataceae in southwestern Hubei has a very close relationship With the same flora in Jiangxi, Jiangsu and Japan.