The flow field of an entrained-flow gasifier was numerically simulated to describe coal gasification process. The standard κ-ε turbulence model and SIMPLE procedure were used with the Primitive-Variable method during computation. In order to investigate the influencing factors on the flow field that may have a great effect on coal gasification process, some parametric studies were performed by changing the gas injection angle, gas inlet diameter, gas inlet velocity, extension in burner length and gasifier geometry. The calculation results showed that the basic patterns of the flow field inside the gasifier were nearly the same with a parabolic distribution irrespective of the change in parameters. There existed an obvious external recirculation zone with axial length less than 1.0 m and a narrow internal recirculation region was observed in the entrance of gasifier inlet. The geometry parameters of the burner, such as the oxygen inlet diameter and angle, influenced the flow field at the inlet region near the burner. But after a certain length along the gasifier, the flow field was nearly the same as that in the basic case.