Flexible Piezoelectric fiber composite actuator Device （FPD） is a promising choice for structural actuation and vibration control applications owing to its excellent performance. However， there are few reports about its intrinsic performance parameters that described the actuation behavior， which limits its widespread use and maximum efficiency. Herein， by analyzing the actuation strain mechanism of FPD， a method is proposed to predict its operational voltage range based on ferroelectric parameters and calcu? late its blocking force based on piezoelectric equation， and the reliability of the method is verified by experimental measurement. Moreover， the influence of the active width on the electromechanical impedance properties and strain actuation performance is in? vestigated. The results show that the prediction for the operational voltage range of FPD from the ferroelectric parameters is reason? able and feasible， and the allowable operational voltage of FPD must be limited between the negative subcoercive voltage and the positive poling voltage. The unsymmetric voltage drive mode can realize large strain and small hysteresis synchronously. The de? duction of the blocking force of FPD based on the piezoelectric equation is effective and reliable， and the blocking force of FPD is proportional to its own piezoelectric coefficient， elastic modulus， cross-sectional area and the applied electric field. Furthermore， the capacitance and actuation capability of FPD increase with increasing the active width， while the impedance decreases， the reso? nant frequency， free strain and hysteresis remain fairly static.