1. A topographical measurement system for a specular object, comprising: a screen including a display plane and a fringe pattern, wherein the fringe pattern is displayed on the display plane, the specular object includes a to-be-measured surface arranged corresponding to the display plane, and the fringe pattern is projected onto the to-be-measured surface of the specular object to reflect and form a virtual image; an image capturing device opposite the to-be-measured surface of the specular object for capturing the virtual image; and an image processing device electrically connected to the image capturing device for calculating a surface profile of the to-be-measured surface according to the virtual image.