Lead-free potassium sodium niobate ceramic, with the nominal composition of K0.5Na0.5NbO3, were synthesized by conventional solid state sintering, and its dielectric, ferroelectric, and piezoelectric properties were characterized as a function of sintering temperature. The orthorhombic to tetragonal phase transition (TO-T) temperature of K0.5Na0.5NbO3 ceramic sample was about 220°C, and its Curie temperature was about 420°C. The high bulk density was obtained for all compositions by solid state sintering in air. Bulk density was increased with temperature and it reached to 4.4 g/cm3. The K0.5Na0.5NbO3 ceramic sample sintered at 1100°C was optimized densification properties. In addition, the ferroelectric loop and dielectric characteristics dependence of different sintering temperature for K0.5Na0.5NbO3 ceramic sample was obtained. Finally, we found that the piezoelectric constant (d33) was 160 pC/N, high remanent polarization (Pr) was 33mC/cm2, and high electromechanical coupling coefficients (kP) was about of 45%.