## 1 Introduction  
Tea is one of the most popular non-alcoholic beverages in the world and its popularity is closely related to its delicious taste and pleasant aroma [1]. Different processing methods contribute to taste and aroma. Tea can be divided into six categories, according to its quality characteristics and processing methods: green tea, white tea, yellow tea, oolong tea, black tea, and dark tea. Among them, oolong is semi-fermented tea, and therefore has both the fragrance of green tea and the mellow taste of black tea. It is also famous for its rich and varied floral fragrance. Dancong tea, which is mainly produced in the Guangdong province, has a long history of cultivation in China. This type of tea includes _Camelia sinensis_ cv. Lingtou Dancong, a national variety in China, whose core production area is the Fenghuang mountain. Oolong tea made from fresh leaves of _C. sinensis_ cv. Lingtou Dancong is loved by consumers because of its unique honey-like flavor. It has been approved as a product with high economic value and a national geographical indication.  
The aroma of oolong tea is affected by many factors before and after harvesting. At the pre-harvest stage, the genotype of the tea variety plays an important role in the aroma of tea products, and the aroma of Dancong tea produced from fresh leaves differs widely among varieties and strains [1; 2; 3]. The growing environment of tea plants is another crucial factor in aroma formation. The ecological environment as a whole (i.e., the combination of light, temperature, and soil conditions) at different altitudes affects the types and contents of aroma compounds in Dancong tea [4]. The turnover process of oolong tea also affects its quality. However, few studies have explored the unique aroma characteristics of tea products made from the Lingtou Dancong cultivar (also known as Baiye Dancong), and whether this special aroma is affected by environmental factors [2].  
Aroma compounds can be extracted using a variety of methods, including solvent extraction and headspace collection, and detected using methods such as gas chromatography-mass spectrometry (GC-MS) and GC-olfactometry (GC-O). These detection methods can be supplemented by statistical analyses and various calculations to analyze aroma compounds in detail [5]. More than 700 aroma compounds have been identified in tea leaves and tea soups, but the aroma characteristics of tea leaves are determined by a few key contributing aroma compounds. Many studies have shown that the human-perceivable odor is related to the threshold and concentration of aroma compounds, so the information obtained by a detector cannot completely reflect the real aroma [5]. Therefore, GC-O/MS is a promising method for fragrance analyses.  
In this study, the aroma components in leaves of Lingtou Dancong oolong tea plants grown at different altitudes were comprehensively analyzed by GC-O/MS. The aroma components of oolong tea grown at different altitudes were identified and quantified, and the reasons for differences in their types and contents among these materials were explored. The overall aim of this study was to determine which compounds are responsible for the honey-like aroma of Lingtou Dancong oolong tea and to provide specific guidance for cultivating tea under the most suitable environmental conditions.