The safety issues caused by sodium dendrites limit the widespread application of sodium metal batteries. Herein, a self-healing polymer electrolyte (SPE) is prepared by immersing the self-healing polymer in a liquid electrolyte. Benefiting from the self-healing properties, elastic interface, and dense nonporous structure of the SPE, the fabricated NaK|MC SPE|NaK symmetric battery presents a long battery life (∼590 h) and low polarization voltage (192 mV). Moreover, the PTCDA|MC SPE|NaK full cell also delivers stable long cycles and outstanding rate performance.