A low-dimensional model for slug elimination is established to improve the applicability and accuracy of current models. Inspired by the flow stages of severe slug flow, the model in this paper is divided into three distinct flow stages—slug growth, liquid production, and blowout stages—to accurately capture the flow behaviors of severe slugging flow. For high-pressure operating conditions, a multiphase valve model considering phase slip and critical flow is analyzed and applied to expand the application boundary of the low-dimensional model. The new model and the state-of-the-art low-dimensional model reported in the literature are compared in detail with the results from experiments and the OLGA simulator. The results show that the new model can well simulate the flow behaviors of SS1 and SS2. In the three validation conditions, the absolute values of the mean relative errors of the new (old) model for the simulation of flow cycle, riser pressure drop, and inlet pressure are 2.67% (103.52%), 6.51% (22.88%), and 2.84% (11.31%), respectively.