In the process of robotic fish design，shape design of fish body and tail fin is very important. In order to study the shape of the whole fish with less fluid resistance and higher propulsion efficiency，three different robotic fish models are established taking tuna，dolphin and sailfish as bionic objects. Boundary conditions are defined using dynamic mesh technology. The hydrodynamic performances such as velocity and fish body force of the three models in the flow field are analyzed by numerical methods. The results show that the sailfish model has the best swimming performance，and the drag force during travelling is smaller than that of the tuna and dolphin models， and the propulsion efficiency of the sailfish model is higher by comparison of Strouhal number. On the other hand， the crescent-fin bionic fish has the highest swimming speed，which is about 2.2 times of the octagonal-fin bionic fish. Therefore，sailfish crescent-finned robotic fish has better swimming performance. The calculation results provide a good reference value for reducing the fluid resistance of the machine fish and improving its propulsion efficiency.