The microstructures and phase constitution of Bi4Ti3O12 toughened PZT ceramics were characterized together with the fracture toughness and piezoelectric properties. By the present approach, the fracture toughness of PZT ceramics was significantly enhanced (K-IC = 2.8 MPa m(1/2)) without dramatic degradation of the piezoelectric performance. The discussion on phase equilibrium concluded that some more stable bismuth layer compounds such as PbBi4Ti4O15 should be adopted as a secondary phase to toughen PZT piezoelectric ceramics, and then the subsequent negative effects on piezoelectric performance might be suppressed.