Abstract: Tremella polysaccharide is the primary component of Tremella fuciformis, and its dissolution behavior significantly influences the physical properties of the polysaccharide. In this paper, utilizing Fick’s second law as a foundation, dissolution kinetic models for hot water extraction (HWE) and pressurized hot water extraction (PHWE) were developed and the relevant parameters were analyzed. Subsequently, the molecular weight of the polysaccharides and the viscosity of the extracted solution were characterized using Gel Permeation Chromatography and a rheometer. Results indicated that the dissolution rate of both HWE and PHWE increased with higher extraction temperatures and longer extraction times. The maximum dissolution rates for HWE and PHWE were determined to be 42.75% and 62.03%, respectively. The dissolution kinetics parameters, including the dissolution rate constant (k), effective diffusion coefficient (D_s), and apparent activation energy (Ea), ranged from 0.0128 to 0.0175 min⁻¹ and 0.057 to 0.1509 min⁻¹, 3.2532 to 4.4348 mm²·min and 2.82 to 6.38 kJ/mol, and 19.49 to 31.43. The linear correlation coefficient (R²) of the kinetic curves for both HWE and PHWE exceeded 0.87, indicating that the dissolution process adhered to Fick’s second law. Additionally, the molecular weight of the polysaccharides decreased with increasing extraction temperature and time, with HWE exhibiting a significantly broader molecular weight distribution range compared to PHWE and higher apparent viscosities.