Low-cost, easy-to-deploy and self-driven flexible electronic devices and flexible sensors will bring new opportunities for developing the internet of things, wearable, and implantable technologies, especially human health monitoring, tactile perception and intelligent robot electronic skin. Therefore, it is necessary to provide high-performance and continuous energy supply modules for flexible electronic devices and flexible sensors. Nanogenerator can achieve high-performance sensing and energy storage characteristics by regulating the polarization electric field at the interface and surface, which is indeed an ideal adaptation choice. In particular, flexible piezoelectric nanogenerator can convert mechanical energy into electrical energy by piezoelectric properties, and can be applied to various deformation conditions such as bending, stretching and compression, which provides a novel solution to the problems of limited energy supply and insufficient performance in flexible electronic and self-driven technology. The piezoelectric output response of piezoelectric nanogenerator can be used not only as an energy signal to self-drive flexible electronic devices, but also as a sensing signal that can be integrated into the self-driven flexible sensors such as gas sensor, pressure sensor and biological sensor. Predictably, self-powered gas sensor with energy harvesting and high-sensitivity sensing, and self-charging power cell with energy harvesting and efficient storage will become hot topics. In this paper, we review the recent developments of flexible piezoelectric nanogenerators in flexible sensors and energy storage devices.