###### Abstract  
Magnesium plays an important role in regulating the growth and quality of tea trees. However, the effect of magnesium regulation on changes in the aroma quality of tea tree leaves remains unknown. In this study, the volatile compounds of tea leaves under different magnesium concentrations were determined to obtain the characteristic volatile compounds that changed significantly and their odor characteristics and to explore the effect of magnesium regulation on the aroma quality of tea leaves. The results showed that magnesium significantly enhanced the content of 15 characteristic volatile compounds in tea tree leaves, especially heptyl formate and t-geraniol. The 15 characteristic volatile compounds mainly showed five kinds of odor characteristics, such as fruity, green, floral, pungent, woody, and burnt; magnesium regulation critically increased floral, fruity, and green odor characteristics. This study lays an important foundation for the application of exogenous magnesium ions to regulate tea aroma quality. eta tree; magnesium regulation; characteristic volatile compounds; odor characteristics 2025140103390/14/0/11/  
the growth of the tea tree root system and increased the leaf starch content but inhibited the accumulation of secondary metabolites, thus affecting the quality of tea tree leaves. Similarly, [PERSON] et al. [10] found that magnesium fertilization could promote the accumulation of theanine and reduce the content of tea polyphenols in tea tree leaves, which made the tea taste more refreshing and reduced bitterness and astringency. [PERSON] et al. [11] explored the effect of magnesium on tea quality with the help of transcriptomics technology and concluded that increasing the magnesium supply would inhibit the accumulation of theanine and caffeine, which in turn was detrimental to the overall quality of tea. Taken together, several studies have shown that although magnesium helps to increase tea yield, it adversely affects the synthesis of major biochemical quality components of tea, such as tea polyphenols, catechins, and caffeine, which may indirectly hinder the enhancement of tea quality. Aroma, as an important characteristic of tea quality, plays a crucial role in the formation and grading of tea quality [12]. In research on the effect of magnesium on tea quality, many scholars have focused on changes in tea biochemical quality indexes after magnesium regulation, which is the basis for evaluating tea quality [8; 9; 11]. However, little research has been reported on the effect of magnesium regulation on tea aroma quality. The formation of tea aroma characteristics and its intensity are closely related to the type and content of volatile compounds in tea tree leaves [13]. By determining the content of volatile compounds in tea tree leaves, the aroma quality of tea can be effectively evaluated [14]. Gas chromatography-mass spectrometry (GC-MS) has shown significant advantages in the determination of volatile compounds due to its excellent performance, and it has been widely used in the analysis of volatile compounds in tea [15]. For example, [PERSON] et al. [16] used GC-MS to analyze the volatile compounds of 22 types of fresh leaves of oolong tea and revealed the main substances responsible for the formation of the aroma differences between different varieties of oolong tea. [PERSON] et al. [17] analyzed the volatile compounds of different aroma types of Longjing tea by GC-MS and identified the key volatile compounds that differentiated between the different aromas.