1. A quick subpixel absolute positioning method, comprising the steps of: (A) capturing a real-time speckle pattern of a target surface; (B) providing a coarse-precision speckle coordinate pattern and a plurality of fine-precision speckle coordinate patterns, wherein the coarse-precision speckle coordinate pattern and the fine-precision speckle coordinate patterns include a coordinate value; and (C) comparing the real-time speckle coordinate pattern with the coarse-precision speckle coordinate pattern by an algorithm and then comparing the real-time speckle coordinate pattern with the fine-precision speckle coordinate patterns to obtain a coordinate value, wherein each said coarse-precision speckle coordinate pattern corresponds to a set of fine-precision speckle coordinate patterns, and the fine-precision speckle coordinate patterns are obtained when the coarse-precision speckle coordinate pattern is captured again and then captured repeatedly according to a fixed fine-precision displacement distance.