Abstract: In response to current issues such as the lack of quantitative analysis of water migration mechanisms during the withering of green tea and the inadequacy of traditional empirical models to precisely regulate moisture and quality, this study innovatively introduces the classic grain adsorption-desorption equilibrium equation (CAE) and the absolute water potential difference equation from the grain industry into the green tea withering process. To achieve dynamic prediction and regulation of the tea withering process, this study established a thermodynamic quantitative model that couples heat-moisture balance, water migration, and quality component transformation. Experiments were conducted using the static gravimetric method on fresh leaves of Longjing 43 from Xiaocun Town, Xianfeng County, Hubei Province, China（108°37′8″～108°46′5″E, 29°19′28″～30°2′54″N）. The adsorption/desorption isotherms were measured across nine supersaturated salt solutions within a temperature range of 10 ℃ to 35 ℃, yielding data on equilibrium relative humidity and equilibrium moisture content. The parameters of the CAE equation for green tea were fitted using Origin software, with constraint premises established based on the physical characteristics of tea leaves (e.g., cell wall composition, polar groups, porosity). Two sets of parameters specific to green tea were derived for adsorption （A₁=6.89, A₂=4.87, B₁=7.32, B₂=5.39, D=204.5）and desorption（A₁=7.12, A₂=5.01, B₁=7.65, B₂=5.68, D=213.2）, respectively. The model fitting accuracy was validated through the following statistical parameters: the SSE values for adsorption/desorption were 1.86 and 2.15, respectively; the R² values for both adsorption and desorption reached 0.998; the RMSE values for adsorption/desorption were 0.203 and 0.221; while the MRE values were 3.12 and 3.78, respectively. These data demonstrate excellent fitting precision of the adsorption/desorption parameters for green tea, indicating that the model can accurately describe the correlation among equilibrium relative humidity (ERH), temperature (t), and equilibrium moisture content (EMC) of green tea. An orthogonal experiment comprising four factors and five levels was designed using Design-Expert V8.0.6.1 software, incorporating the following parameters: withering temperature ranging from 15 ℃ to 35 ℃, relative humidity during withering between 50% and 70%, withering air velocity from 0 m/s to 2.0 m/s, and withering thickness varying from 2cm to 10 cm, resulting in a total of 21 experimental groups. Throughout the withering process, real-time monitoring was conducted for environmental temperature, tea leaf temperature, relative humidity, and mass changes. The absolute water potential difference between the tea leaves and the surrounding environment was calculated, along with the water migration rate (R_w). Pearson correlation analysis, performed using Python software, indicated a highly significant positive correlation between the absolute water potential difference and R_w across all treatment groups (correlation coefficient r ≥ 0.9781, p < 0.05), thereby confirming that the absolute water potential difference acts as the primary thermodynamic driving force for water transport. The content of catechins (C) was subsequently quantified using Agilent 1100 high-performance liquid chromatography. Statistical analysis demonstrated a strong negative correlation between the time-weighted average absolute water potential difference (E_avg) and catechin content (r = -0.8429, p = 0.0001). The linear regression equation can be expressed as C = -0.312×E_avg+104.5. This indicates that catechin content levels increase as E_avg decreases; lower E_avg values correspond to a reduced driving force for water migration, resulting in less oxidation of catechin content and minimized quality deterioration. The underlying mechanism may involve the absolute water potential difference influencing the water migration rate, with water being a crucial factor regulating polyphenol oxidase (PPO) activity. A greater water potential difference leads to faster water evaporation, causing a severe imbalance in osmotic pressure inside and outside the cells. The rapid drying of the tea leaf surface damages the cellular structure, allowing PPO, which is normally confined to organelles, to interact with catechin content in the cytoplasm. This interaction facilitates the binding of enzymes and substrates. PPO catalyzes the dehydrogenation of phenolic hydroxyl groups in catechin content, converting them into polymers and ultimately resulting in reduced detection levels of catechin content. Conversely, a smaller water potential difference allows the tea to maintain appropriate moisture content, preserving the integrity of the cellular structure. In this scenario, PPO remains confined within the cells and is unable to react with substrates, leading to inhibited activity and the retention of more catechin content. The p-value of 0.0001 indicates an extremely significant correlation, ruling out interference from random factors and confirming the reliability of the conclusion. This model transcends the limitations of traditional models that merely describe static equilibrium points, unveiling the synergistic relationships among thermal-humidity balance, moisture migration, and the transformation of quality components during the withering of green tea. Moreover, it elucidates the intrinsic mechanisms by which the absolute water potential difference can indirectly regulate the quality of withered green tea.