In order to realize the high precision calibration of the Los Direction of the RC system camera with small aperture, the establishment of the calibration process coordinate system and the conversion method are discussed, and a new calibration method is provided. The cross-wire is imaged on the CCD image plane by using the theodolite to collimate the beam, the image and the background are separated by using the method of maximum variance between classes, and the centroid of cross-image is extracted by Harris Corner Detection Algorithm, the high precision calibration of the Los of the RC system camera with small aperture is realized. The result shows that the calibration accuracy reaches 1.7″, which is 12 times higher than the traditional theodolite calibration accuracy of 20.9″. It provides a new accurate and feasible method for camera sight axis calibration, and can be applied to other camera sight axis calibration.