In order to simultaneously measure the 3D shape and relative position between two working surfaces of the double-specular-surface objects， we established a common benchmark metrology measurement system based on direct phase measuring deflectometry. To complete system calibration and common benchmark calibration， we designed and fabricated a double-specular-surface calibration plate. First， we calibrated the two subsystems forming the common benchmark morphology measurement system in depth and lateral direction. This established the relationship between absolute phase and depth， pixel coordinates and spatial coordinates X， Y. Next， to avoid the problem of low calibration accuracy caused by the manufacturing error of the double-specular-surface calibration plate， we performed common benchmark calibration to take advantage of the spatial constraint relationship. This allowed us to convert 3D point clouds located in different coordinate systems to a unified coordinate system. Finally， we conducted practical experiments on specular-surface steps and a high-precision measuring block using the common benchmark metrology measurement system. Based on the experimental results， the following conclusions are drawn： the root mean square error of distance between the two surfaces of the measuring block is 0.076 mm， which shown that the proposed common benchmark calibration method is effective in obtaining the double-specular-surface metrology； the maximum absolute error in distance between two adjacent surfaces of the specular surface steps is 0.032 mm， which shown that the error caused by common benchmark calibration reduces the measurement accuracy of the common benchmark metrology measurement system. To improve the accuracy of the common benchmark metrology measurement system， subsequent studies will optimize the common benchmark calibration method.