Dielectric　elastomer　actuators　are　susceptible　to　electromechanical　instability,　limiting　operational　voltages　and　attainable　deformations.　In　this　work,　electromechanical　stability　is　investigated　at　the　example　of　a　cone　dielectric　elastomer　actuator.　Under　the　preload　and　applied　voltage,　deformation　of　cone　actuator　is　inhomogeneous.　The　electromechanical　instability　occurs　when　the　Hessian　of　free-energy　function　of　anyone　particle　in　the　membrane　ceases　to　be　positive　definite.　Critical　voltage　of　the　membrane　decreases　as　the　preload　increases.　The　critical　actuation　stretches　are　proportional　to　the　critical　voltages.　As　the　prestretch　increases,　the　critical　voltage　decreases　while　the　critical　true　electric　field　increases.　These　results　can　be　used　to　guide　the　design　of　cone　actuator.　Copyright　©　(2013)　by　International　Conference　on　Fracture.