Abstract: To solve the numerical control system when handling consecutive micro line segment, frequent start-stop, adding velocity mutation to interpolation problem, through the establishment of circular arc transition switching model, according to the constraint conditions that the turning point in planning out the optimal convergence speed, the transition arc based on the new flexible deceleration control algorithm to track speed forward planning. Through experimental verification, the trajectory error output of the lookahead interpolation algorithm does not exceed the maximum value given by the system, and the velocity and acceleration curves are continuous and smooth, which can not only meet the machining requirements but also maximize the machining efficiency. Achieved the original design of the experiment.