The structural evolution of the BiFeO3-BaTiO3 system is one of the debatable topics in multiferroic solid solutions. We investigate the evolution of the crystal structure and its effect on the multiferroicity of the 0.67(SmxBi1-x)FeO3-0.33BaTiO(3) (0.05 <= x <= 0.2) ceramics. All the 0.67(SmxBi1-x)FeO3-0.33BaTiO(3) ceramics consist of cubic and tetragonal phases within the whole composition range. The structure changes from the cubic Pm3m to the tetragonal P4mm forming a biphasic region and exhibits an interconvertible behavior with the increment of Sm content. The grain size and its uniformity are mainly dominated by the symmetry of the unit cell, and the relative densities change little for all ceramics. The Sm substitution can effectively optimize the ferroelectricity and regulate the macroscopic magnetization. The optimized remnant polarization reaches similar to 6 mu C/cm(2) at x = 0.12 and a maximum remnant magnetization of similar to 0.85 emu/g is observed at x = 0.20. Besides, the varying fractions of the two phases correlate strongly to the enthalpy change which also verifies the appearance of the destroyed ferroelectric state.