The traditional piezoelectric pump has the problems of large flow fluctuation and low flow ratedue to its suction mode and discharge mode. According to these problems, a novel caudal-fin-type valveless pump driven by piezoelectric bimorphs is proposed. Simulating the body structure of tuna, which has the fastest cruise speed among fishes, a vibrator of piezoelectric bimorphs structure is designed. To enhance the performance of the pump, the swing part of the vibrat or is designed to be the shape of flexible leaf blade. The relationship among deformation, natural mode-shape and electromechanical conversion efficiency of cantilever beam piezoelectric laminated structure is analyzed. The prototype is manufactured and the flow rate of the pump is tested. The result shows that when the vibrator works in the second order mode the flow rate reaches 266 ml/min, and the resonant frequencies is 740 Hz; when the vibrator works in the third order mode the flow rate reaches 105ml/min, and the resonant frequencies is 1 280H z.