To fabricate high-performance lead-free piezoelectric ceramics, both the solid-state reaction method and the hydrothermal method were used to synthesize the (K_xNa_1-x)NbO₃ (KNN) lead-free ceramic powders in this work. The ceramic powders were shaped using press forming method at different pressures and the sintering properties of ceramics fabricated from different powders were investigated. Then,the relationship between the account of PVA and the density of ceramics was discussed. The piezoelectric constants of the KNN ceramics polarized at the different voltages, and the dielectric constants against temperatures were also measured. The results show that the powder prepared by hydrothermal method has better sinterability compared to that prepared by solid-state reaction method. Moreover,the addition of K content lowers the sinterability of ceramics. The density of ceramics is very sensitive to the sintering temperature. The K_0.5Na_0.5NbO₃ ceramics fabricated at 1050 ℃ for 2 h has higher d₃₃ (90 pC/N), and its Curie temperature is 410 ℃.