The purpose of this paper is to present a numerical simulation model of a fixed bed gasifier for municipal solid waste (MSW) using ASPEN Plus (Advanced System for Process Engineering Plus) software. The model wasdeveloped based on Gibbs’ free energy minimisation approach and was validated with experimental data of MSW gasification available in literature. Proximate and ultimate analysis of MSW and operation conditions used in the model development are presented and discussed. The study found that simulated and predicted composition of syngas wasin good agreement with experimentally measured data (within 4%). The model can be used to analyse performance of gasification process for varying operating parameters, such as air-fuel ratio, gasifier temperature and moisture content of MSW. This model can be used for other biomass feedstocks, such as wood waste, green waste, food waste etc. to predict the syngas composition at optimised operating condition.