This paper deals with the control of soot emission from acetylene diffusion flames by applying an electric held. The effects of applied voltage, polarity, and spacing of electrodes on soot emissions were investigated experimentally. The results showed that the shape of the flame changed remarkably with increasing applied voltage. The polarity of the applied voltage influenced the shape of the flame and the soot emissions. When a positive voltage was applied to the nozzle electrode, the flame length became shorter and the width at the flame tip was spread at high voltages. More than 90% of the soot emission was suppressed at over 200 kV/m of electric held intensity. Also, the flame temperature increased with increasing applied voltage. In particular, in the case of voltages above 200 kV/m, the temperatures at the flame tip were about 500 degrees C higher than in the absence of an electric held. The rise of flame temperature was caused by the air entrainment promoted by an ionic wind. It was concluded that the soot reduction by applying an electric field was due to the oxidation of soot particles. In contrast, when negative voltages were applied to the nozzle electrode, the efficiency of soot control was limited to about 70% because the flame temperature, even at high applied voltages, was comparable to that in the absence of the electric held.