BOP stack is important device of deepwater drilling riser system. Due to the complex structure of BOP stack, the hydrodynamic coefficients are not accurate by experience or standard recommended as a range, not a determined value. The hydrodynamic coefficients of deepwater BOP stack needs to be analyzed to get more accurate coefficients. The analysis method for hydrodynamic coefficients is introduced in detail based on computational fluid dynamics (CFD) theory. The analysis models are established by large eddy turbulence model (LES). The moving mesh technology is used to simulate the dynamic motion performance of deepwater BOP stack under different current velocity. The hydrodynamic coefficients: drag force coefficient and inertia force coefficient of deepwater BOP stack are obtained. The hydrodynamic coefficients analyses of deepwater BOP stack can provide valuable reference for deepwater drilling engineering applications.