Aiming at the difficulty of single camera system calibration used in cylinder-shaped large forging parts measurement, a new self-calibration method was proposed based on self constraint of the target cylinder-shaped object; the inner and outer parameters of the measurement system were achieved from a single image. Firstly, taking advantage of the rotation characteristics of the cylinder-shaped large forging parts and the supporting shaft, inner parameter constraint equations were established based on circular points and epipolar constraint derived from images of cross sections. And then the full inner matrix of the measurement system was solved using the constraint equations. Secondly, the outer parameter equations were established using the image of rotation axis and cross sections as well as the inner parameters, and the outer parameters were achieved. Experimental results verified the convenience and effectiveness of the proposed method.