Abstract: The two-fluid model is adopted to build one dimensional pressure loss model. The pressure loss is calculated on an air-oil-water multiphase slug flow and the results are compared with the experimental data in horizontal pipeline. In the model presented in the article the pressure loss consists of three terms, including friction pressure loss caused by wall shear stress, viscous loss associated with the eddy motion in the mixing vortex, and the accelerational pressure loss due to gas expansion. The result shows that the model is good agreement with the experimental data. In all cases the largest contribution to the pressure loss is the frictional loss within the slug. However, the additional viscous and accelerational components also exist together, the accelerational term typically accounted for up to 3~5% of the total pressure loss, the viscousloss is up to 2%.