Researchers often improve the energy storage performance of NaNbO3 3 ceramics through doping with Bi-based composites. Recent studies have shown that rare-earth elements, such as La and Sm, can suppress remanent polarization. In this study, a (1-x)NaNbO3-xSm(Mg0.5Zr0.5)O3 x )NaNbO 3- x Sm(Mg 0.5 Zr 0.5 )O 3 ceramic system was designed. Doping with Sm(Mg0.5Zr0.5)O3 0.5 Zr 0.5 )O 3 (SMZ) increases the resistance, activation energy, and bandgap of NaNbO3 3 ceramics, improves the breakdown field strength, and optimizes the energy storage efficiency of NaNbO3 3 ceramics. In this study, 0.92NaNbO3-0.08 3-0.08 SMZ achieved an energy storage density of 4.3/cm3 3 and an energy storage efficiency of 85.6% at 560 kV/cm. When x = 0.15, the sample exhibited an ultrahigh breakdown field strength and energy storage efficiency (720 kV/cm and 91%, respectively). In addition, the 0.08 SMZ sample had an ultrafast release rate of t 0.9 (57 ns), high current density (777.1 A/cm2), 2 ), and high power density (69.93 MW/cm3). 3 ). It has practical application prospects in high-performance energy storage capacitors.