This paper presents a numerical model of synthetic gas inverse diffusion flames. Three typical compositions of synthetic gas, obtained due to variations in the gasification processes, are considered. Inverse diffusion flame consists of a central oxidizer jet and co-flowing annular fuel stream. Fuel flow rate is set such that the power rating remains constant at 1 kW. Air flow rate is incremented systematically to investigate its effects on flame structure and reaction zones. A comprehensive numerical model with variable thermo-physical properties, detailed chemical kinetics mechanism and multi-component diffusion including the Soret effect (thermal diffusion) has been used in the simulations. The numerical model has been validated against the experimental results reported in literature. Based on the composition, in general, based on the amount of nitrogen present in the synthetic gas, in particular, the structure of the flame varies for the same power output. For a given fuel composition, an increase in air velocity increases the flame height in the stable operating regime. Temperature, oxygen, velocity and reaction fields are shown to explain the variations between these flames. © Asia-Pacific Conference on Combustion, ASPACC 2019.All right reserved.