Abstract： According to the relationship between crossratio and angle, a novel linear approach was proposed to determine the  intrinsic parameters of the camera. The image coordinates of the two circular points were derived from two different methods concerning the images of two parallelograms using the Laguerre theorem and the invariance of crossratio. Then the intrinsic parameters of the camera are linearly calibrated from three images of parallelograms according to the circular points which are in the absolute conic(AC). Compared with the calibration method based on rectangles, this approach further weakens the required conditions. Therefore, it has a wide applicability. Extensive simulations and experimental results with real images show that the proposed approach is practicable.