A precision measuring system for tube support plate of steam generator was built, and a parameter measurement method based on edge restriction condition was proposed. Firstly, two-dimensional discrete points were obtained by image processing technology, and the profile was pretreated by calculating the minimum enclosing rectangle of the points. Then, the profile was divided into a series of “extended neighborhood profiles”, and an edge restriction algorithm based on curvature angle was built for precision demarcation. Finally, the profile parameters of part were measured precisely. The experiment results and error analysis show that the measurement precision can reach 0.02mm, which has reference value for the precision measurement of components with complex profile.