Seven new stilbene glycosides including three dimers (<b>1</b>-<b>3</b>) and four monomers (<b>4</b>-<b>7</b>) were isolated from the roots of <i>Polygonum multiflorum</i> along with nine previously identified stilbenes (<b>8</b>-<b>16</b>). In addition, two deglucosylated stilbenes, <b>2a</b> and <b>3a</b>, were also obtained as new dimeric stilbenes. The structures of the purified phytochemicals were elucidated by interpreting their spectroscopic data (NMR, HRMS, and ECD). To the best of our knowledge, this represents the first isolation of a phenylpropanoid (C₆-C₃) substituted with a stilbene unit (<b>7</b>) from the Polygonaceae family. In an in vitro enzyme assay with human recombinant protein tyrosine phosphatase-1B (PTP1B), compounds <b>2</b>-<b>5</b> showed weak PTP1B inhibition with an IC₅₀ value range of 27.4-37.6 μM, while three deglucosylated stilbenes <b>2a</b>, <b>3a</b>, and <b>8a</b> exhibited IC₅₀ values of 2.1, 1.9, and 12.1 μM, respectively. The inhibition modes and binding mechanism of selected inhibitors (<b>2a</b> and <b>3a</b>) were investigated using kinetic methods and molecular docking simulations.