The dielectric elastomer generator (DEG) has attracted attention in converting mechanical energy into electrical energy, due to its high energy density, fast response, and light weight, which together make DEG a promising technology for electromechanical conversion. In this article, recent research papers on DEG are reviewed. First, we present the working principles, parameters, materials, and deformation modes of DEG. Then, we introduce DEG prototypes in the field of collecting mechanical energy, including small-scale applications for wind energy and human motion energy, and large-scale applications for wave energy. At the end of the review, we discuss the challenges and perspectives of DEG. We believe that DEG will play an important role in mechanical energy harvesting in the future.