Abstract: In this work, a new algorithm for performing vapor-liquid-liquid-hydrate multi-flash calculation was developed.Patel-Teja equation of state was used in performing the vapor-liquid-liquid (V-LHC-LW) three-phase flash calculation and Chen-Guo two-step hydrate model was used for calculating the vapor-hydrate phase equilibria.This method was rather simple as it avoided the complexity of simultaneous solution of a sophisticated group of equations.The proposed algorithm was tested on gas-pure water systems, gas-aqueous solution of alcohol systems, gas-aqueous solution of salt systems and gas system containing no free water.The calculation results showed that the proposed algorithm was stable and effective.