Solid polymer electrolytes (SPE) are considered a key material in all-solid Li-ion batteries (SLIBs). However, the poor ion conductivity at room temperature limits its practical applications. In this work, a new composite polymer solid electrolyte based on polyurethane (PU)/LiTFSI-Al 2 O 3 -LiOH materials is proposed. By adding a few inert fillers (Al 2 O 3 ) and active agents (LiOH) into the PU/LiTFSI system, the ion conductivity of the SPE reaches 2 × 10 -3 S cm -1 at room temperature. Exploiting LiFePO 4 (LFP)‖Li as electrodes, the PU-based composite lithium battery is prepared. The experimental result shows that the LFP|SPE|Li displays high specific discharge capacity. The first specific discharge capacities at 0.2C, 0.5C, 1C and 3C are 159.6, 126, 110 and 90.1 mA h g -1 respectively, and the Coulomb efficiency is found to be stable in the region of 92-99% which also shows a desirable cyclic stability after 150 cycles.