Objective To explore the quality change patterns of Ulva prolifera during the hot air drying process.Methods The effects of three key drying factors (hot air temperature, air velocity, and material thickness) on the physical properties of U. prolifera (including moisture content, porosity, specific heat capacity, and thermal conductivity) are systematically investigated. Then, the influence patterns of each factor are clarified by single-factor experiments combined with multi-factor correlation analysis. Finally, a partial least squares regression prediction model is constructed.Results An increase in temperature significantly reduces the moisture content, increases porosity and specific heat capacity, while causing a downward trend in thermal conductivity. An increase in air velocity facilitates water removal and pore structure formation, significantly reducing thermal conductivity. The effect of material thickness on thermal conductivity is the most prominent, as increased thickness inhibits pore structure development. Pearson correlation analysis indicates significant correlations between the physical properties of U. prolifera. A prediction model on physical properties is constructed based on partial least squares, with R² values of 96.8%, 97.6%, 94.2%, and 95.2% for moisture content, porosity, specific heat capacity, and thermal conductivity, respectively. The model fits well and exhibits high accuracy, confirmed to be reliable by the verification test.Conclusion The influence patterns of temperature, air velocity, and material thickness on the physical properties of U. prolifera provide a reference for industrial drying process optimization and quality control.