Abstract: Sulfur deposition is the one of the key issues，which universally exists and must be solved in the process of development of the reservoirs with high sulfur content.The research on the sulfur deposition of the reservoirs with high sulfur content is the foundation of studying sulfur deposition prediction technology of the reservoirs with high sulfur content，precisely handling sulfur deposition dynamic performance in formations and guiding effective development of the reservoirs with high sulfur content.On the basis of analyzing H2S content change law in the process of developing the gas in the gas reservoirs with high sulfur content，the chemical reaction equilibrium theory of inorganic chemistry is introduced to establish formation sulfur saturation calculation method，taking W gas field as example，the amount of element sulfur precipitated from polysulfide decomposition in different distance from wellbore when the formation pressure decreases to different degree is predicted，and comparison between the amount and the total precipitated amount calculated with analytic model is conducted.Result indicates that，in the process of the development of the reservoirs with high sulfur content，under the condition of minor sulfide content change，the sulfur content precipitated from polysulfide （H₂Sx+1） takes very low proportion of total precipitated amount，i.e.，physical deposition is the main way of sulfur deposition，so as the deposition theory of element sulfur is further improved，the solid foundation of recognizing and solving element sulfur deposition in the process of developing the gas reservoirs with high sulfur content and reasonably and effectively developing the reservoirs with high sulfur content is placed.

Key words: gas reservoir with high H2S content, sulfur deposition, mechanism, chemical reaction equilibrium, polysulfide