Abstract: A single actuated bio-mimetic robotic fish is designed based on forced vibration responses of a non-prismatic cantilever which mimick the fish body deformation. The deforming dynamical equations of the fish body during its self-propelled swimming process are developed. Then, the dynamical characteristics of the burst-and-coast swimming mode of the fish are studied by numerical simulations. The simulation results show that higher swimming efficiency can be achieved by changing the ratio between burst time and coast time, which add a new high-efficiency control mode of robotic fish.