Poly (vinylidene fluoride) (PVDF) is a kind of semicrystalline organic polymer piezoelectric material. Adopting processes such as melting crystallization and solution casting, and undergoing post-treatment processes such as annealing, stretching, and polarization, PVDF films with high crystallinity and high piezoelectric response level can be realized. As a polymer material, PVDF shows excellent mechanical properties, chemical stability and biocompatibility, and is light in weight, easily prepared, which can be designed into miniaturized, chip-shaped and integrated devices. It has a wide range of applications in self-powered equipment such as sensors, nanogenerators and currently is a research hotspot for use as flexible wearable or implantable materials. This article mainly introduces the crystal structures, piezoelectric properties and their applications in flexible piezoelectric devices of PVDF materials.