In this paper, three kinds of flexible nanogenerators are introduced, the first one is electrostatic nanogenerator using graphene oxide film, the second one is nanogenerator made of ZnO nanoparticles and multi-wall carbon nanotube with polydimethylsiloxane, the third one is piezoelectric nanogenerator based on a new type piezoelectric material 0.9525(K0.5Na0.5NbO3)-0.0475LiTaO3 (KNN-LTS) nanopowder. These three nanogenerators can be used to harvest energy. Furthermore, these kinds of nanogenerators have some advantages, such as the simple process of fabrication and good flexibility.