Bi4Ti3-xNbxO12+x/2 (BNT) ceramics were prepared by a solid-state reaction method. Effects of Nb doping on dielectric and ferroelectric properties of BNT were investigated. XRD patterns show that Nb5+ substitutions do not change the phase structure. With the increase of Nb doping, dielectric constant and Curie temperature decrease gradually. At the same time, dielectric loss peaks become flatter and dielectric losses become smaller due to the decrease of oxygen vacancies derived from the introduction of Nb5+ at Ti4+ site in BNT. Remanent polarization Pr and coercive field EC of BNT ceramics are both larger than those of BIT without Nb doping. With the increase of Nb doping from 0 to 0.045, Pr increases to the largest value of 17 μC/cm2 and EC decreases to the lowest value of 87 kV/cm, but Pr will decrease when Nb doping content is over 0.045.