A novel layered K4Ag2Sn3S9.2KOH was synthesized solvothermally. A mixture of ethanol and HSCH2CH(SH)CH2OH was used for the synthesis. The HSCH2CH(SH)CH2OH plays an important role and appears to serve as a mineralizer for the solvothermal reaction. A layer comprises Sn3S96- clusters linked by Ag+ ions and possesses two types of 1D channels in which potassium ions are located. The compound crystallizes in the monoclinic P2(1)/m space group [a = 7.8071(2) Angstrom, b = 27.3508(1) Angstrom, c = 10.5008(2) Angstrom, a = 90degrees, beta = 103.874(1)degrees, gamma = 90degrees, Z = 4]. Its crystal structure, composition analysis, and IR are presented.