Incompatibility of electrolytes with Li anode impedes the application of solid-state batteries. Aluminum with appropriate potential, high-capacity, and electronic conductivity can alloy with Li spontaneously and is proposed herein as a carbon-free and binder-free anode of an all-solid-state Li-S battery (LSB). A biphasic lithiation reaction of Al with modest volume change was revealed by in situ characterization. The Li _0.8 Al alloy anode showed excellent compatibility toward the Li ₁₀ GeP ₂ S ₁₂ (LGPS) electrolyte, as verified by the steady Li _0.8 Al-LGPS-Li _0.8 Al cell operation for over 2500 hours at 0.5 mA cm ⁻² . An all-solid-state LSB comprising Li _0.8 Al alloy anode and melting-coated S composite cathode functioned steadily for over 200 cycles with a capacity retention of 93.29%. Furthermore, a Li-S full cell with a low negative-to-positive ratio of 1.125 delivered a specific energy of 541 Wh kg ⁻¹ . This work provides an applicable anode selection for all-solid-state LSBs and promotes their practical procedure.