A new easy technique for calibrating a camera based on circular points is proposed. The proposed technique only requires the camera to observe a newly designed planar calibration pattern (referred to as the model plane hereinafter) which includes a circle and a pencil of lines passing through the circle抯 center, at a few (at least three) different unknown orientations, then all the five intrinsic parameters can be determined linearly. The main point of the proposed technique is that it does not need know metric measurement on the model plane and the corres pondences between points on the model plane and image one,hence it can be done fully automatically.The proposed technique is particularly use for those people who are not familiar with computer vision.Experiments with simulated datawell as well as with real images shoe that the new technique is robust and accurate.