An appropriate amount of (Li,Ce) ions are incorporated into bismuth layer-structured piezoelectric ceramics to reduce the oxygen vacancy concentration, limit the grain growth, and enhance the electrical properties and hardness of the ceramics. The existence of a pseudo-tetragonal phase region, the change in the domain structure, and the increase in the spontaneous polarization promote the enhancement of the piezoelectric properties. Additionally, the conductive mechanism in the high-temperature regions is discussed in terms of the direct-current resistivity. A moderate amount of the (Li,Ce) dopant ions can effectively improve the thermal depoling behavior of CaBi 2 Nb 2 O 9 (CBN)-based ceramics. Consequently, the Ca 0.88 (LiCe) 0.06 Bi 2 Nb 2 O 9 ceramic exhibits an optimal d 33 piezoelectric coefficient of 18.5 pC/N and an excellent thermal depoling behavior. Furthermore, the results of the Vickers indentation hardness test reveal that the hardness of CBN-based ceramics is improved to 3.78 GPa. • Co-doping CaBi 2 Nb 2 O 9 with acceptor - donor ions is studied and analyzed. • Pseudo-tetragonal phase region is conducive to improving electrical property of ceramics. • The relationship between lattice distortion and piezoelectric property is revealed. • The improvement of hardness of CBN ceramics can be ascribed to grains refining.