Subsea gas release and dispersion can cause safety concerns such as fire, explosion or stability loss of floating installations. This paper presents a Computational Fluid Dynamics (CFD) based approach to describe the behavior of underwater gas release and dispersion from subsea gas pipelines leak. The uniqueness of the present study is the integration of estimating subsea gas release rate and predicting rising gas plume. The proposed approach is comprised of two submodels. An equivalent short pipeline model is established to calculate the subsea gas release rate, considering the change of hole size and environmental pressure. A 3D model based on Eulerian-Lagrangian modeling concept is built to predict the rising gas plume, in which bubbles are treated as discrete particles. The validation is carried out by comparing CFD results against experimental data. The underwater gas dispersion simulations include a matrix of scenarios for different gas release rates, water depths, ocean current speeds and leak positions, to study their effects on the behavior of underwater gas plume. The developed CFD model can provide some valuable outputs, e.g., gas release rate, rise time, horizontal dispersion distance and surfacing area size. These results could help to conduct the risk assessment and the emergency planning for accidental leakage of subsea gas pipelines. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.