Abstract: A stereo vision system used in construction robot is presented.Because two area CCDs are adapted in the system,it can orientate the space spot of laser spot center.Configuration of the system,math-model and computational equation is discussed.Using gray mention in data disposal,precise orientation of laser spot center is realized.The precision of the system can be up to 2% through the measuring of different sizes about ellipse,rectangle and triangle,and it isn't affected by the form of laser spot.The experiments illustrate that the system has fine stability.