This article presents a comprehensive study of the effects of the caudal fin shape on the propulsion performance of a candal fin in harmonic heaving and pitching. A numerical simulation based on an unsteady panel method was carried out to analyze the hydrodynamic performance of flapping caudal fins of three shapes (the whale caudal fin with the largest projected area, the dolphin caudal fin with the median projected area, and the tuna caudal fin with the smallest projected area). Then, a series of hydrodynamic experiments for three caudal fin shapes were performed. Both computational and experimental results indicate that the tuna caudal fin produces the highest efficiency. However the mean thrust coefficient of the tuna caudal fin is the smallest. It is found that although the mean thrust coefficient for the tuna caudal fin is not large, the input power of the tuna caudal fin is also quite small.So the tuna caudal fin achieves a high efficiency.