The　Li-O-2　battery　based　on　the　polymer　electrolyte　has　been　considered　as　the　feasible　solution　to　the　safety　issue　derived　from　the　liquid　electrolyte.　However,　the　practical　application　of　the　polymer　electrolyte-based　Li-O-2　battery　is　impeded　by　the　poor　cyclability　and　unsatisfactory　energy　efficiency　caused　by　the　structure　of　the　porous　cathode.　Herein,　an　architecture　of　a　composite　cathode　with　improved　oxidation　kinetics　of　discharge　products　was　designed　by　an　in　situ　method　through　the　polymerization　of　the　electrolyte　precursor　for　the　polymer-based　Li-O-2　battery.　The　composite　cathode　can　provide　sufficient　gas　diffusion　channels,　abundant　reaction　active　sites,　and　continuous　pathways　for　ion　diffusion　and　electron　transport.　Furthermore,　the　oxidation　kinetics　of　nanosized　discharge　products　formed　in　the　composite　cathode　can　be　improved　by　hexamethylphosphoramide　during　the　recharge　process.　The　polymer-based　Li-O-2　batteries　with　the　composite　cathode　demonstrate　highly　reversible　capacity　when　fully　charged　and　a　long　cycle　lifetime　under　a　fixed　capacity　with　low　overpotentials.　Moreover,　the　interface　contact　between　hexamethylphosphoramide　and　the　Li　metal　can　be　stabilized　simultaneously.　Therefore,　the　composite　cathode　architecture　designed　in　this　work　shows　a　promising　application　in　high-performance　polymer-based　Li-O-2　batteries.