<p>Volatile organic compounds (VOCs) tend to be consumed by atmospheric oxidants, resulting in substantial photochemical loss during transport. An observation-based model is used to evaluate the influence of photochemical loss of VOCs on the sensitivity regime and mechanisms of ozone formation. Our results showed that a VOC-limited regime based on the observed VOC concentrations shifted to a transition regime with the photochemical initial concentration of VOCs (PIC-VOCs) in the morning. The net ozone formation rate was underestimated by 3 ppb h<sup>−1</sup> (36 ppb day<sup>−1</sup>) based on the PIC-VOCs. The relative contribution of the RO<sub>2</sub> path to ozone production based on the PIC-VOCs accordingly increased by 13.4 %, particularly, the contribution of alkenes derived RO<sub>2</sub> increased around 10.2 %. The contribution of local photochemistry might be underestimated to both local and regional ozone pollution if the consumed VOCs was not accounted for, and policy-making on ozone pollution prevention should focus on high-reactivity VOCs.</p>