A method of identifying a flange specification based on an augmented reality interface includes steps of: providing a first interface, through which an operator picks real-time images of a flange at different viewing angles, and creating a virtual flange surface according to the real-time images; providing a second interface, through which the operator picks three circumferential points corresponding to the flange, and creating a virtual flange model having a virtual outer diameter; providing a third interface, through which the operator adjusts a virtual pitch circle diameter of the virtual flange model; providing a fourth interface, through which the operator adjusts a virtual thickness of the virtual flange model; providing a fifth interface, through which the operator inputs a count of bolts; and searching a database according to the virtual outer diameter, the virtual pitch circle diameter and the virtual thickness of the virtual flange model to obtain searched results.