In this study, the effects of pulse waveform characteristics on the production of OH radical under atmospheric pressure in a water treatment system have been studied. A solid-state linear transformer driver (LTD), which is capable of generating pulsed power with various waveforms, was used in these experiments. In order to investigate the effect of voltage at the last phase of pulsed streamer discharge on production of OH radical, the nanosecond pulse was separated into two parts, the first part and the last part, and the production of OH radical was evaluated by changing the voltage of last part under condition of the same average input power. As a result, when the voltage of the last part of the pulse is suppressed, the OH radical production yield increased, which means inefficient at the last phase. Then, to evaluate the phenomenon at the last part, the OH radical production yield at the last part only was also measured. The yield increased with an increase of the voltage at the last part. It proves that one of the reasons of inefficiency of the production yield at the last phase is electric field reduction after the primary streamer.