Effects of internals on the fluid dynamics and reaction performance in a pilot-scale slurry bubble column reactor (dc = 0.29 m, h = 4 m) for Fischer-Tropsch synthesis were investigated by CFD simulation in two stages: the first stage with only fluid flow and the second stage coupled with flow, mass transfer and reaction. At the same superficial gas velocity based on free area of column cross-section, the effects of internals on hydrodynamics, such as gas holdup, slurry large-scale recirculation and turbulent viscosity, were analyzed in the first stage. Considering the uncertainty of available mass transfer models, these models were evaluated first. These models differ in magnitude of volumetric mass transfer coefficient and relative mass transfer capacity of H-2 to CO. The simulations indicated that, for the slurry column reactor simulated in this paper, the reaction performances simulated with different mass transfer models are similar, and the reactor is in the reaction-limited regime at the relatively low solid holdup condition. The presence of internals decreases gas holdup and reactant concentrations in the slurry phase but increases the mass transfer and reaction rates. Moreover, the syngas conversion and reactor productivity per unit volume are obviously enhanced with the increase of the number of internals.