To overcome the discontinuity of phase unwrapping caused by noise, in this paper, Canny edge detection algorithm is used to get the real edge of the reconstructed model, a second-order difference function is combined to calculate the edge reliability, and the phase is expanded region by region according to the reliability, so as to achieve the purpose of stable global phase unwrapping. The data points of any row (or column) after phase unwrapping of traditional algorithm and this algorithm are unwrapped, the standard deviations of the two algorithms relative to the original data points are 0.0562 and 0.0121, respectively. At the same time, this algorithm can solve the problem of low stability of phase unwrapping caused by excessive noise in the branch cutting method and the problem of discontinuity layer in the reconstructing model by the least square method, which overcome the noise well and carry out three-dimensional reconstruction.