Cell proliferation plays important roles during metamorphosis in flatfishes. As an epithelial mitogen, epigen can promote cell proliferation in a dose dependent manner via stimulating phosphorylation of the EGFR and downstream signaling molecules such as the mitogen activated protein kinase (MAPK). Q RT PCR result in a previous study showed that epigen expressed higher in early stage of metamorphosis, and became low in climate stage of metamorphosis. To further investigate the relationship between epigen expression and metamorphic events in Paralichthys olivaceus，we employed whole mount in situ hybridization to detect the expressional pattern of epigen gene during metamorphosis. The results indicated that epigen expressed universally in various tissues. The expressional signal of epigen in larvae during pre metamorphosis to Stage E was strong, then became weak after Stage F. It was observed that epigen expressed mainly in gill, liver, intestines, fin, actinost, myotome and epidermis. Tempo spatial expressional patten of epigen gene in P. olivaceus indicates that it might participate in some metamorphic events, particularly in those events that happened during early stages of metamorphosis.