###### Abstract  
Tea is the most popular and widely consumed beverage worldwide, especially black tea. Summer tea has a bitter and stringent taste and low aroma compared to spring tea due to the higher content of polyphenols and lower content of amino acids. Microbial fermentation is routinely used to improve the flavor of various foods. This study analyzed the relationship between the quality of black tea, metabolic characteristics, and microbial communities after microbial stuck fermentation in summer black tea. Stuck fermentation decreased the bittermess, astringency sourness, and freshness, and increased the sweetness, mellowness, and smoothness of summer black tea. The aroma also changed from sweet and floral to fungal, with a significant improvement in overall quality. Metabolomics analysis revealed significant changes in 551 non-volatile and 345 volatile metabolites after fermentation. The contents of compounds with bitter and astingent taste were decreased. Sweet flavor saccharides and aromatic lipids, and acetophenone and isophorone that impart fungal aroma showed a marked increase. These changes are the result of microbial activities, especially the secretion of extracellular enzymes. _Asppergillus_, _Pullresources. Tea quality is assessed based on its fragrance, flavor, and color, all of which are influenced by the composition of volatile and non-volatile ingredients. Catechins, the main class of tea polyphenols, are responsible for the asrtingent and bitter taste of the tea soup, while flavonoids, phenolic acids, caffeine, and organic acids impart acidity, bitterness, and astringency [3]. The major contributors in the tea soup that contribute to its freshness and sweetness are amino acids and saccharides [3]. Some amino acids produce aromatic volatile compounds through enzymatic reactions, Maillard reactions and Strecker degradation. For example, methionine produces a potato-like aroma through Strecker degradation [4]. Microbial fermentation is routinely performed to enhance and modify the taste of food and beverages. For instance, [PERSON] et al. enhanced the aroma of coffee beans by fermenting them with Saccharomyces cerevisiae and _Pichia kluyveri_[5]. Furthermore, [PERSON] et al. showed that fermentation of autumn tea with _Eurotiumcristatum_ not only increased the floral flavor but also reduced the astringency and greatly improved the quality [6]. [PERSON] et al. were able to incorporate herbal, sweet, minty, and floral aromas into the tea by co-refmenting with _E. cristatum_ and _A_spergillus niger [7]. In addition, the fermentation of steamed green tea by \(A\). PW-2 resulted in a decrease in the content of green aromatic volatile compounds and a decrease in the content of metabolites with asrtingent flavors, which may be related to extracellular enzymes such as peroxidase and glycoside hydrolase [8]. [PERSON] et al. also reported significant changes in the color and aroma of instant green tea powder after fermentation with _E. cristatum_[9]. Tea is separated into the categories of green, black, yellow, dark, white, and oolong depending on the processing technique. Dark tea is the most fermented type, and its quality is primarily determined by the microorganisms that enzymatically convert or metabolize tea substances into aromatic compounds [10]. Black tea is the most consumed tea in the world. Compared to spring black tea, summer tea has poor quality but high yield. Therefore, improving the quality of summer black tea is important economically. Only a few studies have reported the use of microorganisms to ferment black tea in order to improve its quality. Summer black tea was fermented using _Cordyceps militaris_ by [PERSON] et al. [11]. They discovered that the level of total polyphenols and total flavonoids was reduced while the level of components with floral and woody scents rose [11].