The invention discloses a method for calibrating a camera in an orthogonal three-coordinate measuring machine. In the calibration of the camera for orthogonal three-coordinate measuring machine, the existing calibration method does not take full advantage of high-accuracy transmission and positioning features of the three-coordinate measuring machine but simply considers the selection of different calibration templates for calibration purpose. In response with such case, the invention proposes a novel calibration method. By using a newly designed template and a commonly used first-order radial distortion model and combining the idea of active vision, the method controls the motion of the camera to calibrate the image center and then utilizes the circle isotropy and 8 control points symmetrical with the circle center to calculate the first-order radial distortion coefficient for the further purpose of determining other internal parameters. Error analysis and experiments prove that the method is highly practical and has high calibration accuracy.