Ferroelectric, magnetic, and magnetoelectric effects for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics have been investigated. The data show that magnetoelectric polarization coefficient, ${alpha}_p$ is due to a linear coupling between polarization and magnetization, and that ${alpha}_p$ is independent of dc magnetic bias and ac magnetic field. The values of ${alpha}_p$ and magnetic induced susceptibility for lanthanum modified $BiFeO_3-PbTiO_3$ ceramics are much larger than those of single $BiFeO_3$ crystal. We believe that the magnetoelectric effect is significantly enhanced by breaking of the cycloidal spin state of a long-period spiral spin structure due to randomly distributed charged imperfections.