Abstract: Piezoactuators are widely used in devices such as precision positioning, adaptive optics and automated robots, however, low electrostrain and low piezoelectric strain coefficient (d₃₃^*) limit its practical application. In order to obtain high electrostrain and reduce the driving field in BF-BT (BiFeO₃-BaTiO₃) based ceramics, a series of trace SnO₂ doped BF-BT samples were prepared by traditional solid-phase sintering method. The phase structure, microstructure, ferroelectric properties and asymmetric electrostrain behavior of 0.7BF-0.3BT-xSnO₂ ceramics after poling an aging were discussed. The research results show that multi-phase coexistence is successfully constructed with the appropriate amount of doping. The strongly polarized directional defect dipoles during aged process will form an internal bias field that tends to promote the effects of external fields when they follow the applied field, thereby resulting in the highly asymmetrical strain behavior along with decreased driving field to obtain a large d₃₃^*. The results show that 0.7% electrostrain and large d₃₃^* = 1 190 pm·V⁻¹ are achieved in 0.7BF-0.3BT-0.2% SnO₂ ceramics.