A multiphase flow calibration semi-closed loop system includes an oil-gas-water separation unit, a multiphase flow calibration unit, a single phase flow calibration section, a gas flow section, a flow data acquisition unit, and a programmable logic controller (PLC). The system is designed to have a two-step calibration process. In a first step, single phase water flow meters and single phase oil flow meters of the system are calibrated independently. In a second step, multiphase flow meters or multiphase water cut meters are calibrated using the pre-calibrated water flow meter, pre-calibrated oil flow meter, and the pre-calibrated gas flow meter. In doing so, the oil-gas-water separation unit, the multiphase flow calibration unit, the single phase flow calibration section, and the gas flow section communicate with the flow data acquisition unit providing real time data. Thus, the PLC connected to the flow data acquisition unit can perform the required calibration processes.