Evolution of crystal structure in Pb1-xBax(Fe1/2Nb1/2)O-3 ceramics has been investigated by X-ray diffraction and Raman spectra analysis together with the dielectric characterization. The crystal structure for all compositions is cubic and the cell volume indicates a sudden change at x=0.075. Pb1-xBax(Fe1/2Nb1/2)O-3 ceramics with x>0.075 are paraelectric, whereas those for x<0.075 are ferroelectric at room temperature. The evolution of phonon modes indicates that the ferroelectricity of Pb1-xBax(Fe1/2Nb1/2)O-3 solid solution ceramics is caused by the off-center Nb5+ in BO6 octahedron. The ferroelectric-related distortion is still observed in paraelectric solid solutions with x>0.075.