Abstract: In the eye-in-hand systems, camera translation can be easily realized and it is a movement needed very often. In this paper, two simple methods are presented to mark the focal length after the camera focal length is adjusted. Then, a method is given to detect the direction of the camera with different focal lengths according to the two images captured before and after motion. In fact, the adjustment of camera focal length is also a translation motion, and translation of the camera at this time is the synthetic result of the two translation motions. Finally, a method is given to solve the translation position of the camera coordinate system caused only by the manipulator translation.