We demonstrate a reliable and highly efficient epitaxial templating approach for the formation of two-dimensional (2D) colloidal crystals. By applying an alternating electric field (AEF), one-dimensional colloidal lines are used as an epitaxial template to site specifically initiate 2D colloidal crystallization and control the orientation of the 2D colloidal crystals. The kinetics of the crystallization and structure ordering is precisely and conveniently manipulated by the external AEF The well-defined artificial linear defects are embedded inside the 2D colloidal crystals by means of heteroepitaxy, whereas the unwanted existing defects are controllably relaxed via an electrically induced annealing process. This epitaxial templating approach is fast, reversible, and amenable for large-area oriented patterning of colloidal crystals, providing a new way for the creation of novel materials and devices with functions and properties that can be reversibly changed, such as electrically tunable photonic waveguides and e-papers.