The magnetoelectric effect can be observed in the composites of magnetostrictive and piezoelectric phases by the the mechanical transfer from one to the other. The large magnetoelectric effect exists in the multiferroic composites with Pb(Zr,Ti)O3 rod arrays embedded in a ferromagnetic medium of (Tb,Dy)Fe2/epoxy. The large magnetoelectric effect and its origin in this structure was discussed on the basis finite element method. The numberical results were close to that of the experiment. The distributions of strain, stress and electric polarization and their relation were analyzed. The authors gave a way to improve the magentoelectric effect based on the distribution of the electric polarization.