Measurement-integrated simulation (MI-simulation) is a numerical simulation in which experimental results are fed back to the simulation. The calculation results become closer to those of experiments even with rough grids. Therefore, the simulation is considered to be suitable for monitoring the state of a pipeline since the calculation time can be significantly shortened. In this paper, the MI-simulation is applied to monitor flow after an orifice plate in a pipeline including unsteady oscillatory condition. The algorithm of the calculation is considered to make it closer to real time simulation. We confirmed that the calculation time could be much shortened by the proposed method compared with that of a general simulation