Sulfide-based conductors are one class of the most promising solid electrolytes for next-generation of all-solid-state batteries due to their advantages on high ionic conductivity and favorable mechanical properties of easy densification. Besides new material chemistry to be explored, understanding the pressure effect on structure and property is equally important from both fundamental and practical considerations, as pressure is one way to tune the properties of such solid electrolytes. Here we report the pressure-driven structural evolution and conductivity change of Na3SbS4 solid electrolyte through the integration of molecular dynamics (MD) simulation and in-situ experiments. Theoretical calculation predicts that no phase transition happens to tetragonal Na3SbS4 under 10 GPa isotopically pressure. Synchrotron X-ray diffraction and Raman results confirm that Na3SbS4 keeps stable tetragonal structure but shows anisotropic compressibility along different directions. After pressure release, the ionic conductivity of Na3SbS4 increases by four folds to 1.6 mS cm−1, which is resulted from the dramatic decrease of grain boundary resistance.