Abstract: The well effluent to be transported consist of three fluids, oil, gas and water. Oil/water liquidoid exists as water-oil emulsion in pipeline of the triphase (oil, gas, water)mixed transportation. The characteristics of mixed transportation of gas phase with water-oil emulsion are: ① various flow patterns; ② high loss of kinetic energy between phases; ③ unsteady flow. The method of flow pattern model is adopted to study the pipeline pressure drop of the triphase mixed transportation according to the characteristics. The calculation method for the pipeline pressure drop of mixed transportation, which the paper introduces with case, consists of the following steps: ① calculating the characteristic parameters of oil, gas and water when transported as a mixure in pipeline; ② calculating pressure.drop △P_g and △P_L when flowing only in single phase; ③ judging flow pattern with Beck flow pattern map for mixed fluid in pipeline; ④ calculating pressure drop of triphase in mixed transportation according to the flow pattern. The calculation method provides study basis for mixed transportation.