<p>Phenolic compounds emitted from biomass burning are important precursors for the formation of aqueous secondary organic aerosols (aqSOA), but there is limited research on the formation mechanisms, product characteristics, and related kinetics, especially on comparative studies under different wavelengths of ultraviolet (UV) light. Therefore, this study selected eugenol (Eug) and acetosyringone (AS) as precursors to investigate the kinetics of aqueous-phase oxidation reactions under two UV light sources (254&#xa0;nm/313&#xa0;nm). The results showed that the pseudo-first-order rate constant, <i>k</i>_obs was highly dependent on pH value, initial phenolic compounds concentration and added H₂O₂ dosages. The ranking of <i>k</i>_obs were <i>k</i>_O2 &gt; <i>k</i>_air &gt; <i>k</i>_N2, indicating that oxygen is beneficial for degradation. Scavenging experiments determined the relative contributions of reactive oxygen species (ROS) and the results showed that both •OH and O₂^•− played significant roles in the photodecay of Eug and AS, with O₂^•− being more prominent. Light-absorbance at 365&#xa0;nm of products increased for the first 7&#xa0;h, and then decreased at the later stage indicated the formation of light-absorbing substances and subsequent photobleaching. Combining the changes in organic acids, oxidative characteristics, and product composition during the reaction, it is speculated that the products of the OH aqueous-phase oxidation of the two phenolic compounds undergo functionalization followed by fragmentation, leading to an increase in oxidation degree. Organic acids are formed through dehydrogenation or ring-opening, further impacting climate change and air quality. This study for the first time compared the reaction rates of the two phenols under 313&#xa0;nm UV light source and comprehensively analyze the products characteristics and mechanisms, which was significant for expanding the atmospheric kinetics database and understanding the chemical activity of phenolic substances in the atmosphere.</p>