A new method for the investigation of dielectric elastomer actuators is developed, in which the relaxation of actuation force is observed under constant strain condition in an open-circuit regime. Independent isothermal surface potential decay measurements were employed to study the charge storage properties of the same elastomer materials. The following materials were used for dielectric elastomer actuators fabrication: VHB (adhesive films by 3M) and Poly-styrene-ethylene-butadiene-styrene (SEBS-Dryflex). It is found that actuation force relaxation kinetics is largely dependent on charge storage and transport properties of the actuator's dielectric elastomer material.