One-dimensional (1D) calibration is one of the most important methods in camera calibration because of its advantages of anti-occlusion and low cost. Firstly, we propose the geometric interpretation of 1D calibration rotating around a fixed point based on the 1D homography matrix. Secondly, it is proved that the cross ratio invariance in projective geometry is equivalent to the 1D homography matrix in the pinhole imaging model. Compared to the cross ratio invarianceof four collinear points, the constraint of 1D homography matrix is more general. Finally, aiming at the 1D calibration under planar motion, the intersection point of two extension lines is calculated by 1D homography matrix. A new convenient method is given to convert planar motion into rotating around a fixed point. The correctness of the proposed algorithm is verified by simulation experiments and real experiments. The experimental results show that the calibration accuracy of the proposed algorithm is improved greatly compared with that of the existing methods.