Product gas composition of biomass gasification was predicted using MS-Excel Solver tool with the method of minimization of Gibbs free energy, which studies only the effect of temperature on equilibrium reaction conditions. The input required for the simulation are operating temperature, elemental analysis of biomass sample and the thermodynamic coefficients of each gas components and elements. Simulation of literature data was performed at temperatures 600 degrees C, 700 degrees C, 800 degrees C, and 900 degrees C. A close match had been observed between the values from literature and the simulated values for incomplete and complete carbon on the basis of root mean square error calculated for each data point.