This study presents a numerical analysis of fluid- structure interaction whose structure is a flexible piezoelectric material. Piezoelectric materials are widely used in aeroelasticity and turbomachinery fields for vibrational, flutter and noise control. In this work a FSI benchmark is revised to contain the piezoelectric materials. The influence of piezoelectricity on the oscillation of the structure and fluid flow is considered. For validation, two benchmark problems are solved and results of the present code are compared with those of the previous works. Current results show that the piezoelectric behavior of a plate significantly influences the oscillation of the plate and the fluid flow properties.