Abstarct: In this thesis in the first step, iron sulfide (FeS) samples with iron / sulfur molar ratio of the same at temperaturs 100 , 120 , and 140 were syntesised by hydrothermal method. Then, samples with iron to sulfur ratios of 2: 1 and 1: 2 at 100 , and also at ratio of 2 to 1 at 140 ° C were prepared. Then the structural, optical, electrical and magnetic properties of the prepared samples were investigated. X-ray diffraction results of all samples confirmed the formation of a tetragonal phase. In samples with the same molar ratio, increasing the synthesis temperature caused reduction in crystallite size. Investigating of the optical properties of the samples showed that their direct band gap varies in the range of 1.56-2 eV. Study of the morphology of the samples showed that the molar ratio of Fe/S affects the size and shape of the grains. Raman spectra of the samples confirmed the tetragonal phase of FeS with a little impuring phase. Hall effect measurements showed that all samples are n-type semiconductor. The magnetic prooperties measurments at room temperature, showed weak ferromagnetic behavior.