A novel biomimetic robotic Boxfish is designed in which pectoral fins are symmetrically assembled on both sides and each one with 2 degrees of freedom can achieve flapping, swaying and the composite motion of them, separately. The hydrodynamic model is established for the robotic fish to cruise by rowing-mode. Through numerical simulation, we analyze and obtain the relations between the swimming speed and the values of the movement parameters including period of motion, swaying amplitude and original phase, etc. Its validity is illustrated by the experimental results. On this basis, the straight swimming mode of the robotic fish with rowing-mode is determined. The presented results shows that the biomimetic robotic fish with rowing-mode can swim with high efficiency and speed.