Abstract: Aerosol liquid water content (ALWC) and acidity (pH) are important indicators to characterize the physical and chemical properties of aerosols, which are of great significance for studying the aerosol generation mechanism and PM_2.5 pollution sources. This study was based on the online monitoring data of PM_2.5 and water-soluble ion components from the State Ecology and Environment Scientific Observation and Research Station for the Yangtze River Delta at Dianshan Lake in 2020. The diurnal and monthly time changes of ALWC and pH, their influencing factors, and their relationship were analyzed using the ISORROPIA-Ⅱ model with positive and metastable system. At the same time, MeteoInfo software was used to simulate the backward trajectory of air masses, and the transmission sources of higher ALWC and pH were explored. The results indicated that: (1) The effects of SO₄²⁻ and NO₃⁻ on aerosol pH were related to their concentrations, proportions, and ALWC, while the impact of NH₄⁺ on pH was limited. NH₄⁺ showed a strong positive correlation with SO₄²⁻ and NO₃⁻, and higher pH tended to approach the fitting curve. (2) ALWC was lower when the concentration of PM_2.5 was below 75 μg/m³. As RH increased with the increase of PM_2.5 concentration, ALWC rose rapidly, especially when RH exceeded 80%. (3) ALWC was highest in January, lowest in August and highest in the afternoon. When the temperature was between 13-27 ℃, its sensitivity to temperature was relatively small, but as the temperature increased, ALWC gradually decreased. (4) pH was higher in winter and lower in summer, with the lowest values occurring in the afternoon of the day, possibly because the temperature increase resulted in a decrease in ALWC and a subsequent decrease in pH. (5) The origin and movement speed of air masses had certain influences on both ALWC and pH. The research shows that the liquid water content and acidity of aerosols in the Yangtze River Delta region are significantly affected by meteorological conditions, and changes in temperature and relative humidity have a positive impact on the physical and chemical properties of aerosols. This study can provide data and theoretical reference for further deepening the understanding of the aerosol generation mechanism in the eastern coastal areas of the Yangtze River Delta.