The work aims to regulate the phase structure of Na0.5Bi0.5TiO3−BaTiO3−SrTiO3 (NBT−BT−ST) ternary ceramics with SrTiO3, to obtain electrostrictive materials of good performance at room temperature, so as to use it in research and development of micro feeding vibrator for packaging machinery. (1−x)[0.94NBT-0.06BT]-xST ceramics were prepared through conventional solid-state reaction method. Based on the analysis of the phase diagram of (1−x)[0.94-NBT-0.06BT]-xST ceramics, the origin of strain property in different phase regions was illustrated. The ferroelectric, strain and electrostrictive behavior of the ceramics with relaxor phase were investigated. With the increase of ST content, the phase structure of (1−x)[0.94-NBT-0.06BT]-xST ceramics underwent the following changes:coexistence of rhombohedral and tetragonal → tetragonal → coexistence of ferroelectric and relaxor → relaxor. The strain of the ceramics in the rhombohedral and tetragonal coexisting region, the ferroelectric and relaxor coexisting region and the relaxor phase region were mainly attributed to the lattice deformation and the non-180o domain switching, the electric-field-induced reversible relaxor to ferroelectric phase transformation and the electrostrictive effect, respectively. With the increase of ST content in the relaxor phase region, the relaxation of (1−x)[0.94-NBT-0.06BT]-xST ceramics enhanced, the ferroelectric hysteresis loop narrowed, while the strain values and hysteresis decreased in varying degrees. The strain hysteresis of the sample with x=0.40 decreased to 7.8% under 60 kV/cm, showing typical electrostrictive characteristics. A high electrostrictive coefficient of 0.021 3 m4/C2 was achieved for the composition with x=0.40 at 50 kV/cm due to the strong relaxation and the formation of polar-nano-regions. The phase structure of NBT based ceramics regulated by ST can effectively improve the electrostrictive property in the relaxor phase region. The electrostrictive materials of ceramics prepared with this technique can provide technical foundation for research, development and improvement of micro actuator for packaging materials.