Abench-scale updraft gasifier was used as a fluidizedand fixed-bed gasification unit in three modes (fluidizedbed at equivalence ratios (ER) =0.2 and 0.25, and a mode in fixed-bed). The experiments were done in five different temperatures (650, 700, 750, 800 and 850oC). To obtain the required data to develop a thermodynamic equilibrium model, the proximate and ultimate analysis were carried out on potato shoot as feedstock. Since the developed model is a temperature-based model, it gives different outcomes in different temperatures. The model gave a completely exact result to predict CH4 in fluidized-bed at ER=0.25. The average error for the difference between each produced gas in experiments and the model showed the best result of the model for CO with the error of just 0.7%. Regarding each experiment data difference with the model data, the model was more accurate to be used in fluidized-bed, especially at ER=0.25 than the other two modes. Moreover, the best performance of the model was obtained for CO, N2 and CO2, according to the average errors. Since the maximum amount of high heating value (HHV) and carbon conversion efficiency (CCE) was observed at higher temperatures, it can be contended that the model has better performance at higher temperatures.