The electrical performances and relaxation behaviors of the Na0.525Bi0.475TiO2.975 and Bi-deficient Na0.525Bi0.475TiO2.975 sample were investigated. The grain conductivity of the Na0.525Bi0.475TiO2.975 sample is able to reach 1.51 x 10(-3) S/CM at 673 K. In the temperature range of measurement, the grain conductivity of the Bideficient Na0.525Bi0.475TiO2.975 sample is lower than that of the Na0.525Bi0.475TiO2.975 sample. By the internal friction and dielectric relaxation spectrum, the activation energy and relaxation time at infinite temperature were determined as (0.82 eV, 2.47 x 10(-14) s), (0.67 eV, 5.82 x 10(-12) s) and (0.85 eV, 5.8 x 10(-13)s), (0.52 eV, 2.55 x 10-10s) for the Na0.525Bi0.475TiO2.975 and Na0.525Bi0.475TiO2.975 samples at the different temperature regions. In the Na0.525Bi0.475Ti02.975 compound, there is larger specific free volume, higher mobile oxygen vacancy content and better oxygen vacancy mobility, which cause the higher grain conductivity in the Na0.525Bi0.475TiO2.975 compound. To some extent, by the Bi-deficient method, oxygen vacancies can be introduced into the Na0.525Bi0.475TiO2.975 compound and the grain conductivity may be improved, but the other side of Bi-deficiency harms the oxygen vacancy diffusion capacities in the Na0.525Bi0.475TiO2.975 compound.