This paper presents an approach for camera auto-calibration from uncalibrated video sequences taken by a hand-held camera. The novelty of this approach lies in that the line parallelism is transformed to the constraints on the absolute quadric during camera autocalibration. This makes some critical cases solvable and the reconstruction more Euclidean. The approach is implemented and validated using simulated data and real image data. The experimental results show the effectiveness of the approach.