Abstract: From Single Particle theory, we derived Simulant equations with rectangular waveguide and obtained calculating formulas of TEmn and TMmn mode.Under the same conditions of calculation, it was shown that the results of the reduced one dimension is the same as those of one dimension.Our results are relatively near to LLNL's when only TE₀₁ mode is considered.With the two dimension code FEL-2-A on the basis of investigating its reliability,we analysed the effect on total output power by wtggler field of different linearly polarized,optical field and electron beam parameters under the conditions of constant wig-gler and different linearly polarized wiggler.These preliminary results will be of some reference value to design and experiment of low energy FEL amplifier.