Metasurface has excellent artificial control ability of electromagnetic (EM) wave, which can be applied in transmission, reflection, diffraction and other propagation scenarios. Therefore, metasurface has great application potential and prospect in the field of basic optics and electromagnetic regulation. Introducing active components into metasurface construction is a key step in the development of the next generation of planar optical components and EM devices. In the past few years, researchers have attempted to develop novel active materials and tunable mechanisms based on metasurface devices to realize various EM properties (such as amplitude, phase, polarization, spatial and temporal responses) and device functions (such as beam steering, dynamic focusing, tunable filters, dynamic holograms, etc.) with dynamic regulatory functions. Although these active metasurfaces show great potentials in practical applications, there still remains some significant challenges. In this review, the potential applications, emerging technologies and research directions of active metasurfaces have been mainly discussed and analyzed.