Abstract: The development of numerically controlled positioner for arc-welding robot is of vital importance to the design of welding flexible manufacturing center (WEMC) of arc-welding robot.The control system has taken 2-aixs servo motor control card as its core and use the two-mode controller that based on Fuzz and PID control method as its position controller.In two-mode controller,the outputs of Fuzz and PID act on object at the same time,but weights of the Fuzz and PID are differ from value of error.The weight of Fuzz controller is big when error is big;on the other hand the weight of PID controller is big when error is small.This structure avoids concussion effectively when from one controller switch to other controller.Two-mode controller has realized the precise control over position of welding positioner.The thesis has made a detailed theoretical analysis of the constitution design and real-time controlled software and brought up the design and fulfillment method of multi-task real-time controlled software of high precisely numerically controlled welding positioner,which has a good result in practice.