The invention designs a precise dynamic monitoring method for fractures of a mining subsidence land and a measuring device. The measuring device comprises steel-bar measuring points respectively fixed at the two sides of a ground surface fracture; small holes are formed in the steel-bar measuring points and are used for erecting instruments for measuring the elevation and a plane coordinate; and the instruments are an electronic level gauge with precision at mm order and a GNSS RTK (Global Navigation Satellite System Real Time Kinematic). The precise dynamic monitoring method and the measuring device designed by the invention have the advantages that the advantages of precise and fast satellite monitoring and optical monitoring and simple and easy implementation of the steel-bar measuring points are fully integrated; the defects that three-dimensional deformation of the fracture cannot be conveniently and accurately measured due to the own defects of structure and accuracy of the device in the existing measuring method for the fractures of the mining subsidence land are overcome, the limitation of the existing measuring method in the use range is avoided, and simultaneously the irreversible disturbance of concrete piles or other fixing devices buried at the two sides of the ground surface fracture is reduced to greatest extent, so that the promotion and practical value is good.