Based on the models of hydrate phase equilibrium in bulk water and porous media,an improved model was proposed to predict the methane hydrate equilibrium in marine sediment environment.In the suggested model,mechanical equilibrium of force between the interfaces in hydrate-liquid-vapor system was considered.When electrolyte was present in pore water,interfacial energy between hydrate and liquid was corrected by an equation that is expressed as the function of temperature and electrolyte concentration.The activity of water is calculated based on the Pitzer model and the interfacial energy between liquid and gas is solved using the Li method.The prediction results show good agreement with the experimental data.By comparison with other models,it is proved that this model can improve the accuracy for predicting hydrate phase equilibrium in marine sediment environment.