In this study, we performed accurate OH measurements as well as selective HO₂ and RO₂ measurements at a rural site in North China Plain with state-of-the-art instruments newly developed. We confirmed the previous discovery on the enhancement of the OH in low NO_x with which little O₃ production was associated, and we found a missing RO₂ source in high NO_x which promoted higher O₃ production. Our results are of vital importance for ozone abatement strategies currently under discussion for China.