Polyether is a kind of ideal polymer matrix for solid polymer electrolytes (SPEs), but its inherent drawbacks (such as the semi-crystalline nature and strong complexation of lithium ions) still hinder their commercial application. The construction of comb-like SPEs effectively increases their functionalities and improves the comprehensive performance. Herein, we apply a dynamic boronic ester exchange strategy to simultaneously enhance the lithium-ion conduction and self-healing ability of the SPEs, thus effectively solving the current problems of polyether. The copolymer (GPA) containing side chains with poly(ethylene glycol) (PEG) and diol groups was obtained through reversible addition–fragmentation chain-transfer (RAFT) polymerization and hydrolysis, and PBA-M2070 containing the boronic acid group and flexible polyether segments was obtained via Schiff base reaction. Boronic ester bonds were formed by dehydration of the diol groups of GPA and the boronic acid groups of PBA-M2070. Dynamic exchange of the boronic ester bonds at the branched sites enhanced the side-chain motion, thus increasing the self-healing ability and electrochemical performance of the SPEs, as well as the cycling stability of assembled batteries. Benefiting from the dynamic boronic ester exchange and enhanced side-chain mobility, the SPEs exhibited self-healing within 10 min and an ionic conductivity of 1.58 × 10–5 S cm–1 at 30 °C. The assembled lithium metal batteries (LMBs) were operated stably at 0.5C for 300 cycles. The dynamic boronic ester exchange strategy used to enhance the LMBs properties provides new insight into the design of comb-like polymer electrolytes.