0.98Na0.5K0.5NbO3 –0.02Bi0.5Na0.5TiO3 (NKNBNT) nano-powder was fabricated by mechanical alloying method. The NKNBNT particle and water molecular on the particle surface became an insulator/ conductor system because of the surface defect and moisture absorption of Na and K ions. A large non-Debye relaxation was found in the range of 250 to 450K in this system. Its dielectric constant is higher 3-4 order of magnitude than that of pure NKN ceramics. This relaxation includes three regions, and the maximum of dielectric constant is near percolation value. This porous composite is expected to be used as a super capacitor or moisture device.