The structure and electrical properties of perovskite layer structured (PLS) (1-x)Sr2Nb2O7-x(Na0.5Bi0.5)TiO3 (SNO-NBT) prepared by solid-state reaction method are investigated. The addition of NBT is beneficial to speed up mass transfer and particle rearrangement during sintering, leading to better sinterability and higher bulk density up to 96.8%. The solid solution limit x in the SNO-NBT system is below 0.03, over which Ti4+ is preferable to aggregate and results in the generation of secondary phase. After the modification by NBT, all SNO-NBT ceramics have a Curie temperature T-c up to over 1300 degrees C and piezoelectric constant d(33) about 1.0pC/N. The breakthrough of piezoelectricity can mainly be attributed to rotation and distortion of oxygen octahedron as well as higher poling electric field resulting from the improved bulk density. This study not only demonstrates how to improve piezoelectricity by NBT addition, but also opens up a new direction to design PLS piezoceramics by introducing appropriate second phase.