Abstract: Severe slug flow occurs in the submarine mixed transportation pipeline between QK18-2 platform and QK18-1 platform in Boxi Oilfield. It is likely to cause the overflow of the separator due to the instability of the slug. In this paper, the submarine pipeline between QK18-2 platform and QK18-1 platform was simulated by OLGA software. It is shown that the pressure at the bottom of the riser and the transient liquid mass flow at the pipe outlet fluctuate violently. In order to prevent the slug flow from damaging the pipeline and the process equipments in the downstream of the pipeline, three control measures (i.e., top throttling method, multiphase pump boosting method and gas lift method) were numerically simulated by OLGA software. It is indicated that these three methods can well control the severe slug flow, The severe slug flow in the submarine pipeline is completely eliminated when the opening of throttle valve is 3%, the multiphase pump is installed at the bottom of the riser, the pressure is increased by 0.5 MPa, and the gas injection rate is 5 kg/s. Based on comprehensive analysis, it is ultimately recommended to adopt the top throttling method with the 10% opening of throttle valve. The research results play an important role in guiding the slug flow control in Boxi Oilfield.