Abstract This study was carried out on identification and density determination of Coelentrate medusae in Doragh and Ghazaleh creeks in Mahshahr area in Khozestan Province (Persian Gulf). Coastal waters from July to June. Monthly sampling were collected from 2 creek with 300µm mesh size plankton net in oblique tow from near bottom to surface.and sample of macro medusae were collected from local fisher man. In general:16 species of medusae were identified belonging to 2 class(Hydromedusae,Scyphomedusae),4order(Leptomedusae,Trachymedusae,Siphonophora,Rhizostomeae),11family(Phialuciidae,Campanulariidae,Eirenidae,Aequoreidae,Geryoniidae,Diphyidae,Rhizostomatidae,Catostylidae,Cassiopeidae)and13genus(Phialucium,Octophialucium,obelia,Phialella,Eirene,Eutima,Aequrea,Liriope,Diphyes,Lensia,Rhizostoma,Catostylus,Cassiopea)..Includes:Phialuciumcarolinae,Eirenekambara,E.hexanemalis,Liriopetetraphylla,Diphyesdisper,D.chamisonis,Obeliasp.,Lensiasubtiloides,Aequreaparva,Phiallelasp.,Eutimalevuka,Octophialucium indicum, O. medium, Cassiopea andromeda, Catostylus perezi, Rhizostoma sp. The frequency and percentage of frequency for each species was measured.The most frequencywasobservedinJuvenilemedusae(38/5%),E.kambara(22/18%),D.chamissonis(11/6%),Ph.carolinae(4/9%)respectively. In this study ,the total abundance of medusae was 610/73No/m3.the mean anoual abundance of medusae was 43/7No/m3.and the most mean abundance of medusae were observwd in March(23/71±8/35No/m3) but there was no medusae in September. Among spicies Eirene kambara was the most dominante spicies in the year study. Comparision frequencies in Doragh and Ghazaleh estuary showed no significant differences. The effect of temperature ,salinity and pH as three main environmental parameter on medusae frequency investigated. Only significant relation was found between medusae frequency and temperature in two creek. Indicies of diversity showed the most diversity of month is March and the less diversity of moth is January. Diversity indices distinguished a median level diversity in medusae population in Western north of Persian Gulf.