The Saloma Lagoon connected to the Okhotsuk Sea by two mouths, is ideal place for the aquaculture of scallops, oyster and other marine products. However, the water quality of half closed area, likes the Saloma Lagoon, easily grows worse. For the maintenance of the water quality and permanent use of the lagoon for the aquaculture, the understanding of the water exchange is necessary. During winter, the lagoon is ice covered and ice floes drift into the lagoon through its two mouths. And ice floes causeserious damage to the aquaculture facilities. In order to prevent such damage, 13 ice booms were constructed at the mouth No.1. Ice floes trapped in ice booms make the ice jam which has large fluid resistance. The water flow in the Saloma lagoon is affected those ice cover and the ice jam. In this study, the effect of ice cover and ice floes on water flow was examined by the numerical simulation of the water flow in the Saloma lagoon is carried out, changing the ice cover and the ice jam conditions.