In the wavefront phase reconstruction with simultaneous phase-shifting interferometers, accurate position registration and determination of object region for phase-shifting interferograms are needed to be done so that the reconstructed accuracy and the successful implement of phase unwrapping algorithm can be assured. A position registration technology based on statistical analysis method is presented to do with the circular simultaneous phase-shifting interferograms. According to all corresponding pixel positions, a variance distribution function is calculated from a group of interference patterns including different phase distributions. By using the maximal interclass variance method, the threshold segmentations are implemented, and so the background and object regions of interferograms can be sperated effectively. Furthermore, the edges of object regions are detected by applying gradient operation. With the improved Hough transform algorithm, absolute positions and radius parameters of each edge are estimated. With numerical simulation, the match precision of this method under the radius of greater than 64 pixel can be achieved up to 0.5 pixel. In addition, a self-referencing simultaneous phase-shifting interferometer is built to validate the reliability and practicability of the proposed method experimentally.