<p>Conventional gel polymer electrolytes based on polymers such as poly(ethylene oxide) face inherent limitations in enhancing ionic conductivity and electrochemical stability. Introducing diverse functional groups into the polymer framework enables the precise modulation of its physicochemical properties, thereby influencing the performance of lithium metal batteries. Herein, an <i>in situ</i> dual-crosslinked gel polymer electrolyte based on polyester and polyamide is proposed. This design enables synergistic cation-anion regulation, facilitating continuous Li⁺ transport by abundant ester groups while anchoring the anions by N–H groups. The resulting gel polymer electrolyte exhibits a high ionic conductivity of 0.58 mS cm⁻¹ and an elevated Li⁺ transference number of 0.6. The assembled Li∥LiNi_0.8Mn_0.1Co_0.1O₂ coin cells achieve 400 cycles at 0.5 C and 300 cycles at 1 C. Furthermore, a 4-layer stacked Li∥LiNi_0.8Mn_0.1Co_0.1O₂ (active material mass loading of 26.7 mg cm⁻²) pouch cell in lean electrolyte conditions (1.7 g Ah⁻¹) is assembled and sustains 45 cycles without obvious decay. This study provides a strategy of synergistic cation-anion regulation in gel polymer electrolytes, offering insights for stable lithium metal batteries.</p>