A parallel mirror calibration method with two calibration modes is presented to calibrate the posed relationship of the camera relative to the screen, which does not have a common field of view in stereo deflectometry. The camera captures images of the screen through the reflection of parallel mirror. The rotation matrix is directly determined by perspective-n-point method and the principle of mirror. The solution to rotation matrix only requires one parallel mirror position, whereas the calibration method with a plane mirror requires at least three plane mirror positions. About the translation matrix, two different calibration modes are proposed: single-camera calibration mode with two parallel mirror positions and dual-calibration mode with one parallel mirror position. The translation matrix in single-camera calibration mode is determined by solving linear equations. The solution of the translation matrix in dual-camera calibration mode is converted into obtaining the optimal value of the distance from the parallel mirror to camera. In addition, the influence of parallel mirror configuration and setup distance about calibration accuracy and precision is analyzed through simulations. The experimental results demonstrate the validity, simplicity, and high precision of the parallel mirror calibration method. Further, dual-camera calibration mode is available for automatic, quick, and high-precision calibration of stereo deflectometry.