With no previous work on gasification of oil palm fronds (OPF), the design of a gasifier with optimum performance for such a biomass can be difficult. Prediction of the optimum operating condition using computer software can avoid costly trial and error designs. The objective of this work is to simulate biomass gasification process in a downdraft gasifier using OPF as a feedstock by means of Aspen Plus software. Three different equilibrium models were proposed using the unit operation models of ASPEN. Prediction of syngas composition obtained from each model was compared with experimental results from literature in order to select the best model that gives more reliable results. The optimum operating conditions that would result in the best composition of syngas was determined based on the prediction of the models. Sensitivity analysis has been carried out to investigate, the effect of temperature (500°C - 1000°C), and equivalence ratio (ER) (0.2 < ER < 0.53), to the resulting composition of syngas. From the work, it is found that rate of production of CO in the syngas increases with temperature, while the trend is decreasing for CO 2. The rate of production of H2 is nearly constant for temperature values above 700°C. In addition, the rate of production of CO2 increases with equivalence ratio while that of H2 is predicted to decrease at higher equivalence ratio. The rate of production of CH2 tends to be only in trace amount for equivalence ratio values above 0.3, while a maximum output of CO is achieved at lower equivalence ratio less than 0.3, and higher oxidation zone temperature value, above 800°C. The simulation results showed that the operating condition would be optimum at higher temperature range of above 800°C, and equivalence ratio value of 0.3. © 2012 American Institute of Physics.