The domain structure and switching behaviors of La3+-doped strontium bismuth tantalite (SBT) thin films on (111) Pt were investigated with vertical piezoresponse mode scanning force microscopy. The switching behaviors were found to be dramatically influenced by the crystal and domain structure. After polarizing by an external electrical field, the reversed domain displayed an expanding in the size in the absence of the external field. The substitution of La3+ for Bi3+ created a high compressive stress in the lattice, and the small orthorhombic distortion causes an easier 908 switching than that of non-doped SBT. Based on these analyses, it could be drawn that the expanding of domain size after lift-off of external field attributed to the 908 domain switching in the La3+-doped SBT thin films.