High ionic resistance at the electrolyte/electrode interfaces is considered as one of the main challenges for developing solid-state lithium metal battery. Herein, the homogeneous and continuous Li+ transport channel is constructed from the cathode to the anode to reduce the solid-solid interface resistance. This strategy is conducted by a surface modification of polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) and Li6.75La3Zr1.75Ta0.25O12 (LLZTO), which are the key components in solid-state electrolyte, with chemically grafting of zwitterionic sulfonate betaine (SB) to endow the ionic conductivity and improve the solid-solid interface compatibility. Therefore, a series of composite solid-state electrolytes were prepared by optimization of the content of polymer matrix (SB-PVDF-HFP), ceramic powder (SB-LLZTO), and lithium salt. The designed composite solid-state electrolyte was used to act as electrolyte membrane and the ion conductive phase in the cathode. The assembled Li/LiFPO4 cell delivered the reversible capacity of 146.6 mAh/g at 1.0 C, higher than the cell without surface modification. Furthermore, the results of molecular dynamics simulation showed that higher diffusion coefficient (D) of Li+ with modified components could promote the creation of fast Li+ transport channel in bulk electrolyte and at the interface, facilitating the electrochemical performances of solid-sate battery.