In this study, cellulase enzyme production by Trichoderma reesei on three lignocellulosic substrates (corn bran, sawdust and wheat bran) and percentage of different combinations of sawdust and wheat bran by solid-state fermentation method for 6 days in scale checked out. Then, under optimal substrate component proportions obtained from Erlenmeyer-scale, the effect of aeration at three levels of 0.5, 1 and 1.5 liters per hour of initial dry substrate (l/(h.gds)) on the production of this enzyme in 0.5-Liter packed-bed bioreactor was studied. The initial substrate moisture and pH were 70 %(w/w) and 5 respectively, and the heating temperature was set at Erlenmeyer-scale and bioreactor at 30 and 28 °C, respectively. Cellulase enzyme production was evaluated based on the activity of endoglucanase and exoglucanase enzymes. The highest amount of endoglucanase and exoglucanase activity at substrate combination of 75% wheat bran and 25% sawdust in Erlenmeyer-scale at day 6 and 3 were obtained 13 and 6.4 U/gds, respectively, and in bioreactor at aeration of 1.5 (l/(h.gds)) at day 3 were attained 36 and 10 U/gds, respectively.