Solid electrolyte is one of the promising electrolytes to realize safe and high energy density rechargeable lithium metal battery. However, in view of the characteristics and defects of the solid inorganic and polymer electrolytes, the high-performance solid electrolyte is still a challenge for effective application in batteries. Herein, we report a novel inorganic-polymer flexible composite electrolyte prepared through synthetic of chelating copolymers. With synergistic coupling, the active filler-Li1.5Al0.5Ge1.5(PO4)3 can be uniformly distributed and maintains good composite with the polymer matrix. Thereby, this composite structure promotes the electrolyte with increased electrochemical stability and enhanced thermal stability. In our case, the larger volume fraction of continuous interface between the filler and gel polymer layer is helpful to increase ionic conductivity and Li+ ion transference number of composite electrolyte. Specifically, a large amount of fillers as a rigid part can block dendrites and provide effective pathways for lithium ion transfer, meanwhile, the uniform distribution of gel polymer layer on the surface of inorganic particles facilitates a soft contact to reduce the interface impedance and a substantial flexibility to adapt the volume change in electrode. For further illustration, the solid-state lithium battery of LiFePO4/Li using this composite electrolyte shows relatively satisfactory performance, indicating the considerable cycling performance and acceptable rate capability. Thus, owing to its easy processing and compelling characteristics, this type of electrolyte make promise to reshape the feasibility of the high safety, stable and high energy density rechargeable solid-state lithium metal batteries at room-temperature.