Destruction and removal efficiency (DRE) of $SF_6$ was tested with low degrees of ionization. The applied dose of ionization energy varied from 63.70 to 212.34 kGy. The initial concentration and flow rate of $SF_6$ gas were 1,000 ppm and 50L/min, respectively. In order to increase the DRE, injection of conditioning agent ($H_2$) were conducted. The DRE of $SF_6$ increased about 2 times with injection of $H_2$ gas.