Solid-state lithium batteries require the high energy density, easy processing and flexibility of electrolyte membranes. However, the low-temperature ionic conductivity and high interfacial impedance are still hindering the further application. Therefore, we developed the solution pouring method by using lithium bis(oxalate)borate (LiBOB) to prepare the PEO/LiBOB/LLZTO solid electrolyte for room-temperature solid-state lithium battery. Compared with the traditional LiPF6 as a lithium additive, the solid-state electrolytes with LiBOB as additive hold higher ionic conductivity and electrochemical window. Moreover, the fabricated solid-state LiFePO4|Li batteries own higher specific capacity and excellent cycle performance at room temperature (165.9 mAhg(-1) with capacity retention of 84.6% after 100 cycles). The large volume of LiBOB could effectively decrease the crystallization state of PEO to improve the conductivity of Li+ ion by the increase in the amorphous region in the whole polymer electrolyte system. This study offers a feasible strategy of preparing solid electrolytes for room-temperature solid-state lithium battery with high performance.