To prevent the rapid release of volatile flavor ethyl isovalerate which was applied in the heated tobacco product(HTPs), a slow-release composite film of ethyl isovalerate was prepared with activated carbon as adsorbent and polylactic acid as coating material. The surface structure of the composite film was observed by scanning electron microscope(SEM), the release property of ethyl isovalerate within the film during heating was evaluated by thermogravimetric analyzer and pyrolysis-GC/MS, and the puff-by-puff release uniformity of ethyl isovalerate from HTPs with the composite film was analyzed using mainstream aerosol online analysis system. Results indicated that the structure of the composite film can prevent the ethyl isovalerate from rapid volatilization. The TG curves showed that the ethyl isovalerate in the composite film could maintain stable till 100 ℃, and can be continuously and uniformly released from the composite film at temperature from 100 ℃ to 300 ℃. Compared to HTPs with directly spraying ethyl isovalerate, the intensity of ethyl isovalerate in the smoke of HTPs with the composite film increased by nearly 90 times, and the ethyl isovalerate can be consistently released till the eighth puff of smoke.