The KxNa1-xNbO3 nanopowders with cubic-like morphology and an average size of about 50 nm were synthesized by sol-gel auto-combustion method. And then, the ceramics were prepared and the phase transition, microstructure and electrical properties of the KxNa1-xNbO3 ceramics were investigated. Pure perovskite phases of the KxNa1-xNbO3 ceramics were confirmed by XRD patterns and the K0.05Na0.50NbO3 ceramics show the coexistence of orthorhombic and monoclinic structures. SEM micrographs show that all samples have bimodal grain size distributions and the number of the small grains decrease with increasing K' content in the bimodal grain size distribution system. The K0.05Na0.50NbO3 ceramics with the uniform grain size and the maximum density show excellent electrical properties with epsilon(r) =467.40, tan delta=0.020, d(33) =128 pC/N and k(p)=0.32 at the room temperature, demonstrating that the properties of the The K0.05Na0.50NbO3 powers prepared by sol-gel auto-combustion are excellent and the ceramics are promising lead-free piezoelectric materials.