Aim:Methodology: Results:Interpretation: Key words:The present investigation was carried out to study seasonal changes in the habitat of Acanthomysis koreana that inhabits the surf zone of Kkotji beach in the west coast of Korean peninsula together with the changes in their fecundity associated with respective sizes of individuals and (most) influential factors affecting the fecundity.Sampling was done during June 2014 -May 2015 with the help of a 50-100 cm depth of the surf zone of Kkotji beach at the time of spring tide.During November to December, 2014, a seasonal change in water temperature was observed wherein the biggest difference in water temperature marked approximately 9℃. The annual level of salinity in the subject area of investigation varied insignificantly. The number of eggs observed therein recorded the highest level in spring and the lowest level in summer. The brooded eggs were higher in spring than summer. The number of eggs in each season exhibited positive correlation with the increasing length of carapace of brooding females. However, the size of eggs in each season showed no significant differences. Fecundity of Acanthomysis koreana was found higher in spring than in autumn.