In this study, the free electron laser (FEL) with a planar wiggler and an ion-channel in a rectangular waveguide is studied for TE waves with numerical simulation. The output power of FEL is obtained self-consistently from the equation of motion and Maxwell's equations. Numerical analysis shows that using the ion-channel, in spite of the magnetic field case [Sakamoto et al., J. Appl. Phys. 75, 36 (1994)], can improve output power in addition to guiding the electrons into the center and prevent dissipation of the beam. Published by AIP Publishing.