Abstract: The path planning problem of manipulators is divided into two steps: the first step is to achieve the optimum path for off line process based on the on line path tracking by adopting the existing approach, cubic spline functions are used for constructing joint trajectories for manipulators; the second step is that an algorithm is developed to schedule the time intervals between each pair of adjacent knots, such that the total traveling time of a manipulator is minimized with the physical constraints on joint velocities, accelerations, jerks.