Abstract: Based on an approximate method, the integral model adapted to the engineering practice, the pressure drop along the pipeline is calculated. Mainly according to the momentum balance equation, the pipeline is divided into independently weenie units which are different from each other in characters and physical parameters. The momentum equation is established in each unit and iterated unit by unite. Compared with the referenced pressure measured by the meter at the end, a preferable simulation of two-phase flow in a pipeline is carried out and the result of the pressure along the pipeline is obtained. Considering the variety of the flow region in different unit and making use of different formula into the momentum equations, errors caused by constant flow region can be avoid.