In order to provide technical support for the design and optimization of the fluid-induced vibration energy harvesting device based on the flexible piezoelectric materials, the piezoelectric properties of the MFC (Macro-Fiber Composite) under the action of bending and swinging was studied. Firstly, the piezoelectric output mechanism of MFC piezoelectric fiber sheet was analyzed theoretically, the piezoelectric model of MFC piezoelectric fiber sheet was established, and various factors affecting the magnitude of the open circuit voltage output of the MFC piezoelectric fiber sheet are obtained. Then a MFC piezoelectric fiber sheet reciprocating bending and swinging test bench based on stepper motor is designed and built, the piezoelectric properties of MFC piezoelectric fiber under different bending angles, bending and swinging speeds, substrates, surface areas and other factors were studied by using the test bench. The results show that the output open-circuit voltage amplitude of MFC piezoelectric fiber increases with the increase of bending angle. When the output voltage amplitude reaches the maximum and the bending angle continues to increase, the output open-circuit voltage amplitude will not change significantly. The output open-circuit voltage amplitude will increase as the surface area of the piezoelectric sheet increase, and the bending swing speed and substrate have no obvious influence on the output open-circuit voltage amplitude.