This paper presents an experimental study on the energy performance of a 50 kWth down-draft gasifier recently developed at Hanoi University of Science and Technology. For this work, charcoal was used as fuel. Under a given value of the total gasifying air (260, 300 and 420 I/min, respectively), air is provided at three intakes located along the height of the gasifier. By such arrangement, the tar content present in the producer gas can be reduced down to 20-37mg/m3. Also, by applying appropriate air ratio for these 3 air-intakes, heating value of the produce gas could be stable at 4.2-4.5 MJ/m3 and thus energy efficiency of the gasifier would be in the order of 62.80 - 71.37 percent.