Aurivillius Na0.5Bi4.5Ti4O15 and Bi4Ti3O12 compounds were synthesized via solid-state reaction tech-nique.X-ray powder diffraction study confirmed monophasic four-layered Na0.5Bi4.5Ti4O15 and three-lay-ered Bi4Ti3O12 ceramics.Dielectric relaxation and con-duction behaviors of Na-contained Na0.5Bi4 5Ti4O15 ceramics were thoroughly investigated in a large scale of temperature of 30-650℃and frequency of 40 Hz-1 MHz.In addition,comparative studies of both the compounds were discussed.Impedance and modulus analyses revealed a single relaxation behavior in Na0.5Bi4.5Ti4O15 compound which was originated from the grain's interior with grain resistance of 2.189×105 Ω and capacitance of 4.268×10-10 F at 570℃.While in Bi4Ti3O12 ceramic the relaxation was due to the contributions of grain and grain boundaries.Alternating current(AC)conductivity analysis revealed the presence of two different conduction regions in both the compounds.Activation energies for the two different conduction mechanisms,i.e.,in low-temper-ature region and in high-temperature region were calcu-lated to be～0.23 and～1.27 eV at 1 kHz for Na0.5Bi4.5Ti4O15 compound and～0.43 eV and～0.97 eV at 1 kHz for Bi4Ti3O12 compound,respectively.The present study of dielectric relaxation and conduction behaviors would be helpful for further investigations of Na0.5Bi4.5Ti4O15-related Aurivillius compounds.