In order to obtain high power density, energy density and safe energy storage lithium ion batteries (LIB) to meet growing demand for electronic products, oxide cathodes have been widely explored in all-solid-state lithium batteries (ASSLB) using sulfide solid electrolyte. However, the electrochemical performances are still not satisfactory, due to the high interfacial resistance caused by severe interfacial instability between sulfide solid electrolyte and oxide cathode, especially Ni-rich oxide cathodes, in charge-discharge process. Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) material at present is one of the most key cathode candidates to achieve the high energy density up to 300 Wh kg−1 in liquid LIB, but rarely investigated in ASSLB using sulfide electrolyte. To design the stable interface between NCM811 and sulfide electrolyte should be extremely necessary. In this work, in view of our previous work, LiNbO3 coating with about 1 wt% content is adopted to improve the interfacial stability and the electrochemical performances of NCM811 cathode in ASSLB using Li10GeP2S12 solid electrolyte. Consequently, LiNbO3-coated NCM811 cathode displays the higher discharge capacity and rate performance than the reported oxide electrodes in ASSLB using sulfide solid electrolyte to our knowledge.