Solvent-assisted ball milling is used to prepare the sulfide solid electrolyte Li7P3S11. Comparing with dry ball milling and simple liquid phase synthesis, solvent-assisted ball milling can significantly promote the reaction of the starting materials from tens of hours to only several hours. When using dimethoxyethane as the assistant solvent, relatively pure Li7P3S11 with ionic conductivity of 1.0 x 10(-4) S/cm can be synthesized after 8-hour ball milling with following 2-hour 180 degrees C vacuum drying and 4-hour 230 degrees C heat treatment. It is revealed that the transition from the precursor to Li7P3S11 is a two-step process, with an intermediate composed of a thio-LISICON III analogous phase and an amorphous phase. This work not only provides a synthesis route of Li7P3S11 which reduces synthesis duration, but also offers an instructive insight into the phase evolution in solvent-based synthesis process of sulfide solid electrolytes.