The as-prepared BiFeO3 ceramic shows a piezoelectric d(33) coefficient of -14pC/N, that is, an obvious ferroelectric self-poling phenomenon. The temperature gradient between the two surfaces of BiFeO3 ceramic was intentionally enlarged when BiFeO3 was prepared with a rapid liquid sintering method. This temperature gradient and the corresponding thermal strain can introduce defect dipoles through separating bismuth vacancies from oxygen vacancies. A mass of these dipoles introduce a macroscopic internal electric field (E-in) which downward poles BiFeO3 ceramic during its cooling down process. As expected, an E-in of >10kV/cm is confirmed by the asymmetrical polarization/strain versus electric field curves.