1. A three-dimensional data registration method for vision measurement in a flow style based on a double-sided target comprises: A. Setting up two digital cameras which can observe the entire measured object; B. Calibrating intrinsic parameters and a transformation between two digital camera coordinate frames, then establishing a global coordinate frame; C. A double-sided target being placed near a measured area of the measured object, and the two digital cameras and a vision sensor taking images of at least three non-collinear feature points of the double-sided target; D. Removing the target, measuring the measured area using the vision sensor; E. Respectively computing the three dimensional coordinates in the global coordinate frame of at least three feature points in the images taken by the two digital cameras and in the vision sensor coordinate frame of at least three feature points in the images taken by the vision sensor; F. Estimating the transformation from the vision sensor coordinate frame to the global coordinate frame through the three-dimensional coordinates of three or more non-collinear feature points obtained at step E, then transforming the three-dimensional data of the measured area to the global coordinate system; and G. Repeating step C, D, E and F, then completing three-dimensional data registration for all measured areas.