Abstract: This paper focuses on investigating the axisymmetric out-of plane nonlinear deformation of an actuator made of electro-active polymer membrane and designed by American Artificial Muscle Inc.. The essential part of the actuator is a layer of annular electro-active polymer membrane sandwiched between two compliant electrodes. The mechanical model describing the axisymmetric nonlinear deformation of such annular membrane is formulated, and the equilibrium equations characterizing the large deformation of the annular membrane subject to a concentrated force and a voltage are derived by thermodynamics. The derived state equations are solved by using shooting method. The obtained numerical results show that the deformation field in the membrane is highly inhomogeneous. The deformation near the central part of the membrane is large while the deformation near the edge of the membrane is small, which leads to the induced electric field in the membrane where the deformation increases monotonically from the edge to the central part and reaches the maximum at the central part of the membrane. Due to the inhomogeneity of deformation field, the membrane material is not utilized efficiently, which results in material waste.