By researching on the main factors affecting the active zone area strain of electroactive dielectric elastomers, the suitable conditions of area strain for the material in the application as artificial muscles actuator was determined. In the experiments, the strain characteristics of the material was investigated under uniaxial pre-stretching, uniform biaxial pre-stretching and non-uniform biaxial pre-stretching respectively. In addition, the strain rates of the materials active zone under different ratio of the active zone to the window radius of the materials were investigated. The experimental results show that the area strain of active zone would have inflexion under any pre-stretching condition, and the area strain increased with applied voltage increasing, decreased with the ratio of the active zone to the window radius increasing. It could be found that the strain conditions have an important influence on the area strain of the active zone.