<p>Gas-particle partitioning of water-soluble organic compounds plays a significant role in the formation and source apportionment of organic aerosols, but is poorly characterized. In this work, gas- and particle-phase concentrations of isoprene oxidation products (C5-alkene triols and 2-methylterols), levoglucosan, and sugar polyols were measured simultaneously at a suburban site of the western Yangtze River Delta in east China. All target polyols were primarily distributed into the particle phase (85.9–99.8 %), and their average particle-phase fractions were not strictly dependent on vapor pressures. Moreover, the measurement-based partitioning coefficients (<i>K</i><sub>p,OM</sub>) of isoprene oxidation products and levoglucosan were 10<sup>2</sup> to 10<sup>4</sup> times larger than their predicted <i>K</i><sub>p,OM</sub> based on the equilibrium absorptive partitioning model. These are likely attributed to the hygroscopic properties of polyol tracers and high aerosol liquid water (ALW) concentrations (~20 µg m<sup>−3</sup>) of the study location. Due to the large gaps (up to 10<sup>7</sup>) between measurement-based effective Henry's law coefficients (<i>K</i><sub>H,e</sub>) and predicted values in pure water (<i>K</i><sub>H,w</sub>), the gas-particle partitioning of polyol tracers could not be depicted using Henry's law alone either. The regressions of log (<i>K</i><sub>H,w</sub>/<i>K</i><sub>H,e</sub>) versus molality of major water-soluble components in ALW indicated that sulfate ions (<q>salting-in effect</q>) and water-soluble organic carbon can promote the partitioning of polyol tracers into the aqueous phase. These results suggest a partitioning mechanism of enhanced aqueous-phase uptake for polyol tracers, which partly reveals the discrepancy between observation and modeling of secondary organic aerosols.</p>