Abstract: In the present work, the performance of an updraft gasifier was investigated experimentally and numerically. This study aimed to use a two-dimensional model using a code, namely COMMENT code, to investigate the gasification and combustion processes while taking into consideration the process rate within the gasifier. In the present model the kinetic theory of granular flow (KTGF) was introduced to simulate the solid phase, while gas phase turbulence was modeled under k–ɛ model. The predicted temperature and gas composition profiles are in good agreement with the experimental work obtained from the updraft gasifier at the Royal Institute of Technology (KTH). These results show that the present model is a promising tool for simulating the gasification/combustion process of biomass within the gasifier.