Inspired by the diverse properties of hydrogen sulfide, iron sulfide, and iron hydrides, we combine first-principles calculations with structure prediction to find stable structures of Fe-S-H ternary compounds with various FexSyHz (x = 1-2; y = 1-2; z = 1-6) compositions under high pressure with the aim of finding novel functional materials. It is found that Fe2SH3 composition stabilizes into an orthorhombic structure with Cmc21 symmetry, whose remarkable feature is that it contains dumbbell-type Fe with an Fe-Fe distance of 2.435 Å at 100 GPa, and S and H atoms directly bond with the Fe atoms exhibiting ionic bonding. The high density of states at the Fermi level, mainly coming from the contribution of Fe-3d, indicates that it satisfies the Stoner ferromagnetic condition. Notably, its ferromagnetic ordering gradually decreases with increasing pressure, and eventually collapses at a pressure of 173 GPa. As a consequence, magnetic and nonmagnetic transition can be achieved by controlling the pressure. In addition, there is a very weak electron-phonon coupling in Cmc21-structured Fe2SH3. The different superconducting mechanisms between Fe2SH3 and H3S were compared and analyzed.