In　this　paper,　SnS　films　were　cathodically　electrodeposited　on　ITO　glass　substrates　from　aqueous　solution　containing　5mM　SnSO4　and　25mM　Na2S2O3　with　pH　of　2-3.　When　the　deposition　potential　(E)　was　varied　from　-0.60　to　-1.1V　vs　SCE,　the　corresponding　SnS　films　were　characterized　with　X-ray　diffractograms,　microstructure　and　composition　analysis.　It　was　found　that,　the　composition　ratio　Sn/S　of　the　film　varied　with　E,　the　ratio　Sn/S　significantly　increased　and　exceeded　1　at　E　more　cathodic　than　-0.75V　vs　SCE,　and　the　ratio　Sn/S　significantly　decreased　and　was　less　than　1　at　E　larger　than　-0.7V　vs　SCE.　The　stoichiometric　SnS　film　was　synthesized　at-0.72-0.75V　vs　SCE　.　The　structural　and　optical　properties　of　the　film　have　been　studied.　The　X-ray　diffraction　pattern　of　the　film　showed　that　it　was　polycrystalline　and　of　orthorhombic　structure.　The　estimated　optical　bandgap　energy　was　1.31eV.