Ceramics 0.94(K0.5Na0.5)NbO3-0.06LiNbO(3):Er/xYb with x = 0, 0.002, 0.004, 0.006, 0.008 were fabricated in this study, and phase structure, dielectric, piezoelectric, ferroelectric, and upconversion photoluminescence properties of the ceramics were systematically studied. Results show that all ceramics are in the polymorphic phase transition region near room temperature. However, a relaxor-like phase transition was observed as Yb increasing to over x = 0.004. The optimized dielectric, piezoelectric, and ferroelectric properties, and maximized photoluminescence intensity ratio are obtained at x = 0.004. And the electrical and photoluminescence properties of the ceramics were discussed from the point view of the normal to relaxor-like ferroelectric phase transition. The present study demonstrates that both the electrical and upconversion photoluminescence properties of the ceramics have an intimate correlation with the normal to relaxor-like ferroelectric transition induced by Yb doping.