In this work, Li7La3Zr2O12 (LLZO)-based membrane electrolyte, which has good flexibility and can be easily mass-produced, is proposed to address the intrinsic defects of ceramic electrolytes. The LLZO-based membrane electrolyte is electrochemically stable in the voltage range of 0-5.2 V vs. Li/Li+ due to the good oxidative stability of LLZO. We also develop a simple and low-cost approach to fabricate the all-solid-state lithium battery (ASSLB). Wet coating and hot pressing are applied to form a continuous and homogeneous electrolyte layer on a cathode layer. Thanks to the integrated preparation process, there is no obvious interface between the cathode layer and the electrolyte layer, hence reducing the interface resistance. The Li/LiFePO4 batteries exhibit desirable cycling performance at 60 degrees C, which deliver a maximum discharge specific capacity of 151.6 mAh.g(-1) at 0.1C and maintain 97.8% of the capacity after 50 cycles.