For conventional phase measuring deflectometry, the measurement principle based on the law of reflection makes it difficult to perform full-aperture measurements of the radius of curvature (ROC) of large dynamic curvature value. Therefore, the traditional monoscopic deflectometry combined with a planar mirror measurement method is proposed. However, the measurement method of the existing method requires the plane mirror mounted on the monitor to be strictly tilted at 45° and the angle of 45° with the camera optical axis in the horizontal direction, which undoubtedly makes the experimental setup more difficult to align. Therefore, the calibration of entrance pupil center of the imaging lens method is proposed in this paper. In the experiment, only the translation of the display is needed to obtain the position of entrance pupil center of the imaging camera lens, without the need to accurately align the posture of the camera and the plane mirror. Finally, a convex spherical optical element with a mean ROC of 8.262 mm is measured in the experiment, and the mean ROC at each point is measured to be 8.321 mm with a PV of 0.212 mm, with a relative error of 0.71% about. Compared with existing normal incident optical paths, the adjustment process is less difficult, but the measurement accuracy of components is still high, which verifies the feasibility of the method.