Abstract: A new method for optical coordinate measuring is proposed by using the angel between the ray emitted from CCD pixel and optical axis. The two-dimensional checkerboard reference act as a calibration target and the coordinates of the aperture and corner points of the checkerboard can be measured. The ray emitted from a pixel which goes through the aperture intersects a corner point on the checkerboard and project to planes in the world coordinate system, and the angle between the ray and camera axis can be worked out. From one picture, the corner coordinates on image coordinate system can be obtained by the Harris corner detection algorithm and the whole frame coordinates can be determined by interpolation algorithm. According to the principle of pinhole camera, the angel between the ray emitted from pixels on CCD and ray axis can be got, and then the space coordinates by the angel can be determined. Experimental results show that this method has a high accuracy. Since we only need to take a single picture, it's can perform online measurements.