In this study, we optimized conditions of extraction of essential oil from lemongrass (Cymbopogon citratus) stalks and leaves, using steam distillation device having an extent of 25 ÷ 30 kilograms of material per batch and approaching industrial scale. Using response surface methodology (RSM) with three factors that affect to the volume of essential oil obtained (mL/kg): material size (mm), water/material ratio (L/kg) and distillation time (minute). In the optimal condition of lemon grass essential oil distillation using steam distillation at 5.66 L water to 1 kg sample, 10.00 mm material thickness size in 180 minutes, the maximum essential oil volume obtained was 2.98±0.02 mL/kg.