This paper presents a design, modeling and control of a novel wave energy converter (WEC) using Dielectric electro active polymer (DEAP). Application of DEAP in WEC has attracted a lot of works due to development of renewable energy and increasing of human energy demand. However, various challenges of the WEC using DEAP must be overcome before going to realistic application. Firstly, stretch ratio has significant influence on energy conversion efficiency of DEAP. It cannot exceed the limitation value due to mechanical or electrical breakdown, whereas small stretch ratio reduces the energy conversion efficiency significant. Secondly, WEC has to be controlled to maximize the absorbed energy. Therefore, this study employs an innovative device which can adjust the inertia of the floating buoy. A variable inertia hydraulic flywheel is attached on the main thrust shaft to control stretch ratio based on change in the hydrodynamic behavior of the system. A proportional–integral–derivative (PID) controller is designed to optimize stretch ratio under different regular waves. Consequently, the overall energy conversion efficiency of the proposed WEC can reach up to 25%.