The photo-excitation of brown carbon (BrC) form excited triplet states of organic compounds (3C*) upon irradiation, which initiates the photosensitivity reaction occurring at the interface of aqueous aerosol, where the organic compounds may interact with gases or VOCs. However, the driving mechanism of SO2 multiphase oxidation at the air-water interface remains unclear and controversial due to the complex process and poorly kinetic information. Here, we aim to exploring the photosensitized uptake of SO2 on aqueous film and characterizing photosensitive products on the surface. In this study, multiphase reactivities are illuminated by uptake coefficient (γ) of SO2 using a Wetted-Wall Flow Tube (WWFT) in the dark and in the UVB (300-340nm). Aromatic carbonyls (like Vanillin, VL) and Humic acid sodium salt(HA), as photosensitizer (Ph), are the main model compounds from biomass burning. The reactivity on VL and HA were characterized based on decay kinetics. The uptake coefficient (γ) on VL (0.05-1mM) and HA film(50-150mg/l) had a significant enhancement under irradiation, and no dark reaction was observed. That confirmed the introduction of Ph generated 3VL*/3HA* and promoted enhancements in the photochemical process. Gas diffusion limitation is present in this system, and is more prominent at high concentration. Once corrected, γ as a linear relationship with concentration of VL and HA. Eventually, the reactive rate of VL (1.38×109 M-1. s-1) was calculated to be higher than HA (4.78×107 M-1. s-1). Moreover, 1-octanol as a surfactant was introduced into film and led more 3VL*/3HA* concentrating on the surface which showed a significant surfactant effect both on VL and HA. It further confirmed the dominant driven role of excited triplet states in SO2 multiphase oxidation at the surface. To demonstrate this idea, the products of reaction will be measured by HPLC-HESI-MS to reveal multiphase reaction mechanism. Overall, this work reveals the importance of photosensitized reactions in the tropospheric condensed phase (i.e., cloud droplets and aerosols). It is a key for us to better understand and respond to the impact of biomass burning particulate matter on climate change.