Abstract: In order to solve the problem that how to keep the thermal effect constant during the procedure of laser heat treatment on a cam,a so-called algorithm,instantaneous concentric reducing tee algorithm(ICRTA) was put forward to control the laser spot moving at an uniform velocity.It can be realized under three presuppositions,i.e.,the relative speed keeps the same when laser spot scans the curved surface of the workpiece,the distance between the focused laser spot and the profile of the workpiece keeps unchanged,the laser beam is incident along the normal direction of the work piece surface all the time.The surface of the work piece contour and the corresponding points of equidistant line have the same center point at the same time.For a certain constant scan speed at the work piece contour surface,the speed of laser head at the corresponding point of equidistant line can be calculated,so that the movement of the laser head can be controlled.Simulation results with MATLAB show the algorithm is feasible.