Demagnetization is one of the noticeable problems in almost every permanent magnet linear generator (PMLG) for oceanic wave energy conversion. To avoid the degradation of electrical power generation capability, a PMLG with a new feature of variable air gap length is proposed in this paper. To verify the effectiveness of the proposed method, a PMLG has been designed which is simulated for both the fixed and variable air gaps. The finite element analysis is performed for simulation for analysis of the PMLG with the conventional and the proposed methods by using the software package ANSYS/Ansoft. The voltage, current, power, magnetic flux density, and force components of the PMLG are analyzed and discussed. The simulation results show that the new method can effectively avoid the demagnetization problem.