Numerical study of the slurry gasification process inside of Texaco entrained-flow coal gasifier was carried out in this paper. The Eulerian-Lagrangian approach was used for calculating the gas-solid two-phase flow. And the complicated slurry gasification process was divided into several stages, such as slurry-water evaporation, coal devolatilization, heterogeneous reactions and homogeneous reactions, coupled with the changes of particle size. The predicted result of product gas compositions was in well agreement with the experimental data in literature, which verified the validity of the model. The simulation results indicated that there exist four main reaction zones inside of the gasifier which are evaporation/devolatilization zone, combustion zone, reduction zone and outlet zone. The content of effective compositions (CO + H2) in product gas increases with the increasing slurry concentration. The calculation is helpful for designing the operating conditions of the gasifier.