Numbers of hydrate-based new techniques require the algorithm to be able to perform multiphase flash calculation where one phase is a gas hydrate phase.Tetrahydrofuran(THF)is frequently used as a thermodynamic promoter in the development of hydrate-based technique,which can reduce the hydrate formation pressure,especially when methane or hydrogen exists.However,it is a hard work to describe accurately the phase behavior of THF-water system due to their polarities.It has been proved that the water-in-oil(W/O)emulsion can raise the hydrate formation rate and improve the single stage separation efficiency,and furthermore prevent the hydrate from agglomeration to plug the facilities.The goal of this work is to present an extension of our previous work to the prediction of the vapor-liquid-liquid-hydrate equilibrium of such complex systems.These include ternary and quaternary mixtures with W/O emulsion containing THF.The proposed algorithm of four phase equilibrium calculation is very simple due to avoiding the complexity of simultaneous solution of the sophisticated equation group.The calculation results were found to be in satisfactory agreement with the experimental data. Numbers of hydrate-based new techniques require the algorithm to be able to perform multiphase flash calculation where one phase is a gas hydrate phase. Tetrahydrofuran (THF) is frequently used as a thermodynamic promoter in the development of hydrate-based technique, which can reduce the hydrate formation pressure, especially when methane or hydrogen exists. However, it is a hard work to describe accurately the phase behavior of THF-water system due to their polarities. It has been proved that the water-in-oil (W / O ) emulsion can raise the single stage separation efficiency, and than prevent the hydrate from agglomeration to plug the facilities. The goal of this work is to present an extension of our previous work to the prediction of the vapor-liquid -liquid-hydrate equilibrium of such complex systems. These include ternary and quaternary mixtures with W / O emulsion containing THF. The proposed algorithm of four phase equilibrium calculation is very simple e due to avoiding the complexity of simultaneous solution of the sophisticated equation group. the calculation results were found to be in satisfactory agreement with the experimental data.