The invention provides a three-coordinate measuring method of a blade with a T-shaped root, which solves the problems of data instability and inaccuracy due to inadequate point-getting position of measuring points. The method comprises the following steps of: (1) providing a virtual blade for a three-coordinate measuring process through UG (Unigraphics) and automatically coinciding a measuring coordinate system and a virtual blade coordinate system after a virtual blade model is guided into a three-coordinate measuring system; (2)carrying out rough building reference; (3) carrying out digital-analog fitting; and (4) repeating the digital-analog fitting process if the coincidence degree does not meet the requirement after the digital-analog fitting is finished. The three-coordinate measuring method is characterized in that the radius of iteration error in rough building reference is 0.1mm; and the selecting of measuring points in the digital-analog fitting comprises the steps of selecting three measuring points on the radial surface of the T-shaped root of the blade, respectively selecting 1-2 measuring points on two working surfaces of the root and respectively selecting measuring points at steam inlet and outlet sides of the root.