Ferroelectric Sr2Bi4-xDyxTi5O18 (SBDT-x, x= 0—0.20) ceramic samples were prepared using the conventional solid-state reaction method. x-ray diffraction patterns (XRD) of SBDT-x ceramics show that doping with a small amount of Dy does not change the crystal structur e of Sr2Bi4Ti5O18 (SBTi). Their Curi e temperature (Tc) and dielectric loss (tanδ) decrease with Dy dopin g amount. The remnant polarization (2Pr) of SBDT-x increases at first , then decreases with increasing of Dy content. When Dy content is 0.01, the 2Pr reaches a maximum value of 20.1 μC·cm-2. The variation of 2Pr for SBDT-x relates to space charge density, internal strain an d structure distortion. (Bi2O2)2+ layer acting as an insulating layer and space charge storage plays an important role in their ferroelectric properties in BLSFs. The incorporation of doping ions into (Bi2O2)2+ layer may destroy its original function and deteriorate the ferroelectric property.