The effect of blueberry leaves polyphenols on the thermal decomposition of trimethylamine oxide in squid supernatant was studied， and the reaction mechanism was also explored. The results showed that the polyphenols from blueberry leaves inhibited the thermal decomposition of trimethylamine oxide， and reduced the contents of trimethylamine， dimethylamine and formaldehyde. The inhibition of blueberry leaves polyphenols was more significant at higher concentrations of polyphenols. As temperature was increased， polyphenols from blueberry leaves significantly inhibited the thermal decomposition of trimethylamine oxide. When the heating time was lower than 60 min， the inhibitory effect was significant. Free radicals produced during the thermal decomposition of trimethylamine Oxide. Blueberry leaves polyphenols inhibited the production of free radicals. Blueberry leaves polyphenols suppressed the generation of formaldehyde by inhibiting the formation of free radicals.