Abstract: In this paper, cellulose diacetate (CDA) was employed as the skeleton material and polyethylene glycol (PEG) as the phase change material to fabricate a PEG/CDA membrane composite cooling material via solvent blending and membrane casting. The effects of casting thickness, drying conditions, and casting solution composition on the physicochemical properties and cooling performance of the composite were investigated. The optimal preparation process was as follows: 1.6 g PEG₁₅₀₀ and 1.0 g CDA were dissolved in 7.4 g acetone, and the mixture was stirred and refluxed in a 75 ℃ water bath for 6 h to obtain the casting solution. A membrane casting instrument spread the solution into a 400 μm liquid film on a clean glass plate, which was then dried at room temperature for 12 h in a drying oven to yield the PEG₁₅₀₀/CDA composite. Subsequently, the composite was cut into 160 mm × 16 mm strips and folded to form cooling elements. These elements stably reduced the mainstream smoke temperature of heated tobacco products from 67 ℃ to 42 ℃ and the tipping paper temperature from 59 ℃ to 50 ℃, demonstrating excellent operational safety and promising industrial application prospects. In the composite, PEG₁₅₀₀ is uniformly loaded in the CDA-derived skeleton network. During the smoking of heated tobacco products, PEG₁₅₀₀ crystals in the network absorb heat via phase change, while the CDA network restricts the thermal motion of PEG₁₅₀₀ within a confined space. Consequently, PEG₁₅₀₀ does not leak, exhibiting solid-solid phase change characteristics under macroscopic conditions.