In pursuit of miniaturization in the semiconductor industry, two-dimensional (2D) materials are used to fabricate new electronic devices. The topological insulator (TI) material bismuth telluride (Bi₂Te₃), as an emerging 2D material, has potential applications in electronic and spintronic devices due to its unique electrical properties. It is well known that the surface-to-volume ratio increases as the thickness of the material decreases, resulting in a more prominent edge effect. Therefore, for a single-layer Bi₂Te₃, the atomic structure of the edge plays a crucial role in its electrical properties. Here, combining first-principles calculations and in situ transmission electron microscopy (TEM) experimental studies, we report that there are two types of edge structures in single-layer Bi₂Te₃: semiconducting flat edges and metallic zigzag edges. The dynamic evolution process of the edge structure with atomic resolution shows that the proportions of these two edges change with continuous electron beam irradiation. Our findings demonstrate the viability to use electron beam as an effective tool to precisely tailor the edge of Bi₂Te₃ with desired properties, which paves the way for implementation of single-layer Bi₂Te₃ in electronics and spintronics.