Ras is mainly involved in the epidermal growth factor family regulating the signaling pathway of cell proliferation.To investigate the relationship between ras-2 expression and metamorphosis in Paralichthys olivaceus, the full length cDNA of ras-2 gene with 2 384 bp was obtained by rapid amplification of cDNA ends (RACE). The ras-2 gene encodes 187 amino acids with typical structure such as switchⅠ, switchⅡ, P loop and CAAX box, sharing 96.3% sequence similarity with another flatfish Platichthys flesus. RT-qPCR revealed that ras-2 gene was expressed universally in adult Paralichthys olivaceus. The highest expression of ras-2 was found in the fin, while the lowest expression in the muscle. During metamophosis of Paralichthys olivaceus, expressional level of ras-2 gene was decreasing significantly. The whole mount RNA in situ hybridization further showed the expression pattern of ras-2 during metamorphosis of Paralichthys olivaceus and revealed its expression mainly in the epidermal tissues located in fin, jaw, orbit, nostril, lateral line and so on. Higher expression signals were observed mainly in fin, lateral line, jaw and gill during metamorphosis. Since Ras MAPK pathway is well known in regulating cell proliferation, based on expressional pattern of ras-2 gene, we postulate that ras-2 might participate in eye migration and development of lateral line, dorsal fin and gill via regulating epidermic cell proliferation during metamorphosis of Paralichthys olivaceus.