The (0.9 x)Bi0.5Na0.5TiO3-xBaTiO3-0.1K0.5Na0.5NbO3 [BNBKN(x), x=0.060, 0.063, 0.066, and 0.069] ceramics were fabricated by the conventional sintering technique. The P-E hysteresis loops measured under 5 kV/mm at room temperature show that the BNBKN(0.063) ceramics obtain the maximum (Ps Pr) value of 20.6 mu C/cm2 and the largest energy-storage density W of 0.424 J/cm3. In addition, calculation from the X-ray diffraction results shows that the BNBKN(0.063) ceramics are featured with the largest c/a ratio of 0.70887. The W is observed to increase with the increase of the c/a ratio in the BNBKN(x) ceramics. The c/a ratio can be regarded as a significant factor for W in the BNBKN(x) ceramics.