Abstract: This paper studies in particular the relationships between the following three CS(coordinates systems) in a vi-sion system of a general multi-joint"hand-eye" robot: (1) CS of the base; (2) CS of the object; (3) CS of the image.By utilizing the projection transformation and mapping etc. as mediums, we derived out some mathematical rela-tions between the camera image point and corresponding space point in a "hand-eye" robot system. Meanwhileabout fixed type some explorations have also been made. A simple and practical algorithm has been derived out for acurrately and quickly leading the robot to properpoint in space.