The flexoelectric effect is a mechanical-electric coupling effect between strain gradient and electric polarization (i.e., positive flexoelectric effect) or electric field strength gradient and mechanical strain (i.e., converse flexoelectric effect). Unlike the piezoelectric effect, the flexoelectric effect, which is not limited by material symmetry and the Curie temperature, increases with decreasing the material size, thus attracting much attention and having a promising application. This review introduced the history of flexoelectric effect, measurement of flexoelectric coefficient, and mechanism to enhance flexoelectric effect. Recent studies on its application in the realm of sensors, actuators, mechanical memories, flexoelectric piezoelectric composites, energy harvesters, and electronic devices were highlighted. In addition, the further development of flexoelectric effect was also prospected.