Predicting the solubility of elemental sulfur in natural gas is an important task in the prevention of sulfur deposition. The knowledge of the sulfur solution mechanism in hydrogen sulfide is of great help for establishing an accurate model of sulfur solubility. In this paper, a comprehensive model is established based on phase equilibrium theory considering both the physical sulfur solution in hydrogen sulfide and the chemical reaction between sulfur and hydrogen sulfide. In this model, a new vapor pressure expression of elemental sulfur and a new formula for the binary interaction coefficient between sulfur and hydrogen sulfide, considering both temperature and solvent density, are proposed. Our new model can adapt to lower temperature, and the threshold value can be as low as 273.15 K. Furthermore, we find that our model can better fit the experimental data of elemental sulfur in hydrogen sulfide. By analyzing the sulfur solution mechanism in hydrogen sulfide under conditions of transmission, we found that the solution mechanism is mainly driven by the chemical solution when the pressure is above 5.0 MPa, and it is determined by both the physical solution and the chemical solution when pressure is below 5.0 MPa. In addition, increasing temperature can facilitate the physical solution and inhibit the chemical reaction below pressures of 5.0 MPa, but temperature has little effect on the sulfur solution mechanism at pres sures above 5.0 MPa.