Olive flounder (PParalichthys olivaceus), a marine demersal flatfish species, exhibits timid and depressive-like characteristics. Adult olive flounder bury themselves in the sand and present motionless behavior. However, the detail mechanism of regulating the motionless behavior is not fully understood. In this study, using adult group (AG) and juvenile group (JG) flounder as a model, we compared the locomotor activity of AG and JG flounder, and analyzed the transcriptomic expression profiles in the spinal cord by RNA-seq methods.