The limited triple-phase boundaries (TPBs) in solid-state cathodes (SSCs) and high resistance imposed by solid electrolytes (SEs) make the achievement of high-performance all-solid-state lithium-oxygen (ASS Li-O2) batteries a challenge. Herein, an adjustable-porosity plastic crystal electrolyte (PCE) has been fabricated by employing a thermally induced phase separation (TIPS) technique to overcome the above tricky issues. The SSC produced through the in-situ introduction of the porous PCE on the surface of the active material, facilitates the simultaneous transfer of Li+/e−, as well as ensures fast flow of O2, forming continuous and abundant TPBs. The high Li+ conductivity, softness, and adhesion of the dense PCE significantly reduce the battery resistance to 115 Ω. As a result, the ASS Li-O2 battery based on this adjustable-porosity PCE exhibits superior performances with high specific capacity (5963 mAh g−1), good rate capability, and stable cycling life up to 130 cycles at 32 °C. This novel design and exciting results could open a new avenue for ASS Li-O2 batteries.