Lead-free potassium sodium niobate-based piezoelectric ceramics (1-y)(Na0.5-0.5xK0.5-0.5xLix)NbO3-yBiScO(3) ( y=0.01, x=0-0.06) have been prepared by an ordinary sintering process. The XRD analysis showed that the structure changes from orthorhombic to tetragonal with the increase of x (at y=0.01, abbreviated as KNNBSL100x). At room temperature, the polymorphic phase transition from the orthorhombic to the tetragonal phase was identified at approximately 0.02 < x < 0.04. The piezoelectric and ferroelectric properties were significantly enhanced. The temperature dependences of the relative permittivity revealed that the Curie temperature was increased with the addition of LiNbO3. These solid solution ceramics are promising as potential lead-free candidate materials.