Dielectric elastomer transducers with large deformation, high energy output, light weight and low cost have been drawing great interest from both the research and industry communities, and shown potential for versatile applications in biomimetics, dynamics, robotics and energy harvesting. However, in addition to multiple failure modes such as electrical breakdown, electromechanical instability, loss-of- tension and fatigue, the performance of dielectric elastomer transducers are also strongly influenced by the hyperelastic and viscoelastic properties of the material. Also, the interplay among these material properties and the failure modes is rather difficult to predict. Therefore, in order to provide guidelines for the optimal design of dielectric elastomer transducers, it is essential to first develop accurate and reliable models, and efficient numerical methods to investigate their performance. First, this thesis purposes a boundary- constraint method to eliminate the electromechanical instability of dielectric elastomer actuators under voltage-control loading condition and improve their actuation deformation. Second, based on the finite-deformation viscoelasticity model, the natural frequency tuning process of viscoelastic dielectric elastomer resonators is examined in this work. It is found that the tuned natural frequency is highly affected by the material viscoelasticity. Also, it is concluded that the electrical loading rate only influences the tunable frequency range and the safe operation voltage of the resonator, but not the tuned natural frequency when the applied voltage is within the safe range. Third, with the finite-deformation viscoelasticity model, the energy conversion efficiency of dielectric elastomer generators under equi-biaxial loading is also investigated in this work. Simulation results show that increasing the maximum stretch ratio and the rate of defor mation, and choosing a proper bias voltage can lead to an improvement of the energy conversion efficiency. Furthermore, the fatigue life of dielectric elastomer devices under cyclic loading is explored in this work for the first time . Simulation results have demonstrated that the energy conversion efficiency of dielectric elastomer generators is compromised by their fatigue life. To tackle the critical challenges for the development and design of dielectric elastomers transducers, this research develops theoretical models and numerical methods that are able to capture the nonlinear electromechanical coupling, the material properties, the typical failure modes and different operating conditions of dielectric elastomer transducers. With more accurate and reliable modeling methods, this work is expected to provide a comprehensive understanding on the fundamentals and technologies of dielectric elastomer transducers and trigger more innovative and optimal design of such devices.