Abstract: Taking the traveling wave equation of the fish body as a dynamic basis and according to the motion function equation of the fish tail, carangiform robotic fish named"BLRF-I"series were designed. Because of modular design in the robotic fish, the number of tail driving motors can be expediently changed and the difference among the single-link, two-link and three-link biomimetic robotic fish is only the number of tail driving motors. The cruising speed and minimum turning radius experimental results of the robotic fish show that the cruising speed grows with the number of tail driving motors increasing and the minimum turning radius reaches its minimum value while the number of tail driving motors is two, demonstrating that the number of joints has effect on the cruising performance of the robotic fish. The relation equation between the number of joints and the swimming velocity was proposed.