Abstract: For exploding foil initiation system (EFIs), an experimental method based on the piezoelectric film (PVDF) was established to estimate the instantaneous velocity of a flyer. The average velocity of a flyer was measured using a PVDF and compared with the theoretical results of the one-dimensional flyer velocity model. The errors of flyer average velocities are within 10%, indicating that the one-dimensional velocity model meets the calculation accuracy requirements. Meanwhile, relationship between average velocity and instantaneous velocity of flyer was analyzed based on theoretical calculations, indicating that instantaneous velocity of flyer is nearly in proportion to average velocity (v=Δv/0.86). Thus, PVDF film method can be utilized to evaluate instantaneous velocity of flyer.