In this paper, highly pure Na0.5K0.5NbO3 nanopowder was prepared from an economical sol-gel method. Using the nanopowder, dense Na0.5K0.5NbO3 ceramics with ultrafine grain sizes in the range of 200-600 nm were fabricated successfully by low-temperature solid-state sintering at 1085 degrees C for 4 h. The ultrafine-grained ceramics exhibited fine ferroelectric, piezoelectric, and dielectric characteristics. Its room temperature d(33), K-p, epsilon T-33/epsilon(0) at 1 kHz, tan delta and relative density are 154 pC/N, 30.5%, 407%, 0.0155%, and 96.8%, respectively. The results indicate that it is considerably potential to synthesize ultrafine-grained doped potassium-sodium niobate ceramics with excellent properties by using of nanopowder prepared from the sol-gel method.