Non-thermal plasma processing using a pulsed electrical discharge has been investigated as an alternative method for the degradation of organic compounds contained in water. The active species produced by the electrical discharge may play an important role in degrading organic compounds in water, Three types of electrical discharge formed by the needle-plate electrode system were used in this investigation. The degradation of phenol by electrical discharge with the effects of the addition of gas bubbling and chemicals on degradation efficiency was investigated. The results showed that the degradation rate of phenol was affected by electrical discharge types and oxygen gas bubbling. The addition of a small amount of hydrogen peroxide greatly increased the degradation rate of phenol, in which the ultraviolet light from discharge plasma was considered to be a cause of effective degradation.