Previous studies show that near linearity exists between displacement and charge of piezoelectric actuators,while studies under higher fields are lacking and long-time displacement self-sensing is still a challenge.Here we indicate that precise,long-time displacement self-sensing can be accomplished using the Sawyer-Tower circuit,where a high-impedance electrometer and a non-leaky capacitor are used to measure the charge.Calibrating the results on a piezoelectric unimorph cantilever shows that the displacement resolution of charge self-sensing is ～3 nm,much better than that of ～40 nm for the calibrating laser sensor.Testing results under a unipolar field up to 2 k V/mm with different periods indicate that a direct proportional relationship holds between charge and displacement with the maximum error of 4.65％.The self-sensing time can be over 20 min or even longer if a higher-impedance electrometer is used.