The main object of the present invention is to provide a new and general wet-chemical synthesis method to prepare various Li2S and P2S5 based sulfide solid electrolytes (SSEs) materials with high Li+ conductivity for solid state Li batteries. This invention solves the large scale preparation issue of sulfide solid electrolyte materials with small size and high Li+ conductivity, and also present a general method to prepare a series of important sulfide solid electrolyte materials with such characteristics, such as Li3PS4, Li7P3S11 and Li7PS6.