Abstract: 2，6-dichloro-1，4-benzoquinone（2，6-DCBQ）is a novel disinfection byproduct found in tap and swimming pool water，which is widely distributed and toxic， presenting a potential threat to human health. To explore the correlation between 2，6- DCBQ-induced cardiotoxicity and carbohydrate metabolism in organisms and its toxicological mechanisms，we investigated the morphological changes of heart and thyroid tissues of grass carp（Ctenopharyngodon idella）juveniles exposed to 2，6-DCBQ at different concentrations and times and measured the levels of carbohydrate metabolism-related hormones and the activities of related enzymes. The results showed that 2，6-DCBQ could induce cardiac pericardial edema and interstitial edema in juvenile fish，as well as the loss of thyroid follicular glial and epithelial cell proliferation. The exposure also interfered with the levels of the thyroid hormones T3 and insulin in the blood. The activities of some enzymes， such as hexokinase， fructose phosphokinase， and pyruvate kinase， were significantly reduced due to the exposure. Combined with the targeted metabolomics analysis， we inferred that after 2，6-DCBQ exposure，the activity of hexokinase in heart tissue had been inhibited，therefore interfering with the glycolysis pathway ；the conversion of α - ketoglutarate to succinate was blocked，thus affecting the tricarboxylic acid cycle in fish. This study contributes to a further understanding of the toxicological mechanisms of halobenzoquinone disinfection by-products and a comprehensive assessment of their health risks.

Key words: grass carp, halobenzoquinone, heart；carbohydrate metabolism, metabolomics