In order to accurately measure the sight axis of the single axis photoelectric measuring system, based on the invariability of the point on principal optical axis of linear CCD imaging position when the object distance varies, a measurement method of sight axis on cooperative target is presented, and its theoretical derivation is done. Fix the cooperative target in a position, and place the uniaxial optical measuring system on a movable horizontal platform. While mobile the uniaxial optical measurement system follows the slideway, it will only change the distance between the optical measuring system to cooperative target, without changing the height between the axis of optical and cooperation target. Finally, conduct an experiment use of a practical photoelectric measuring system and cooperation objectives. The experimental results show that the accuracy of the measurement method can achieve -0.84".