Abstract: A 2-D magnetic field distribution of a electromagnetic wiggler has been given numerically by solving Poisons's equation.The parameters affecting the peak magnetic field 0.are discussed quantitatively,including the configuration of magnet poles.the size of gap,the wavelength and the current exciting the magnet poles.In comparison with an ideal wiggler.the 2-D field region can be divided into three parts.They are called good,medialand bad region.respectively.This can help us determine the controlled extent of radius of the beam entering the wiggler.The 2-D magnetic field calculation results show that a good configuration of magnet poles can increase the value of B.and suppress saturation in the poles.This conclusion is in agreement with the analysis result given by K.Halbach.According to the nonunifor-mity of 2-D magnetic field distribution and the comparison of the field with the satura-tion magnetic induction B.a further basis for selecting magnet pole configuration can be.provided.On the basis of 2-D numerical calculation of the magnetic field of electromagnetic wiggler.the question of adapting PALADIN wiggler (PW) to the electron beam of 3-5 MeV is discussed.For the electron beam,it is desired that the peak magnetic field can reach 0.4T and the magnetic gap is large enough to install the waveguide.For attaining above specifications,a substantial modification of PW is necessary.The noteworthy respects have been investigated preliminarily in this paper,including adopting the high B,material to make the magnet poles,increasing wavelength decreasing the gap using a elliptical waveguide of instead the rectangular and selecting the pole configuration.