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<i>Camellia taliensis</i> (W. W. Smith) Melchior, belonging to the genus <i>Camellia</i> sect. <i>Thea</i>., is mainly distributed from northern Myanmar to western and southwestern Yunnan province of China, and its leaves have been used to make various teas by the locals of its growing regions. The chemical constituents of <i>C. taliensis</i> are significantly related to those of cultivated tea plants, <i>C. sinensis</i> and <i>C. sinensis</i> var. <i>assamica</i>. The HPLC-ESI-MS analysis of black tea prepared from the leaves of <i>C. taliensis</i> showed a rich existence of polyphenols. Further comprehensive chemical study led to the separation and recognition of 32 compounds (<b>1</b>–<b>32</b>), including one new hydrolyzable tannin, 1-<i>O</i>-galloyl-4,6-tetrahydroxydibenzofurandicarboxyl-<i>β</i>-D-glucopyranose (<b>1</b>), and one new natural product (<b>24</b>). The known compounds referred to seven hydrolyzable tannins (<b>2</b>–<b>8</b>), 10 flavonols and glycosides (<b>9</b>–<b>18</b>), and 14 simple phenolics (<b>19</b>–<b>32</b>). Their structures were elucidated by comprehensive spectroscopic analyses. Among them, 20 compounds (<b>2</b>, <b>3</b>, <b>6</b>, <b>7</b>, <b>8</b>, <b>15</b>, <b>17</b>, <b>18</b>, <b>20</b>–<b>22</b>, <b>24</b>–<b>32</b>) were isolated from black tea for the first time. Most isolates displayed obvious antioxidant activities on DPPH and ABTS⁺ assays, and the hydrolyzable tannins <b>1</b>, <b>3</b>–<b>5</b>, <b>7,</b> and <b>8</b> exhibited stronger inhibitory activities on <i>α</i>-glycosidase than quercetin and acarbose (IC₅₀ = 5.75 and 223.30 μM, respectively), with IC₅₀ values ranging from 0.67 to 2.01 μM.