The invention discloses a reciprocating type numerical control cored string ball tension control method. The reciprocating type numerical control cored string ball tension control method comprises the following steps that a controller receives a first signal, and a set command is sent to an air cylinder according to the first signal, wherein the air cylinder is used for driving a position sensor to move; the air cylinder receives the set command to drive the position sensor to move towards the side away from a balance position; the controller receives a second signal sent by the position sensor and sends a drive command to a drive device according to the second signal, wherein the second signal comprises data of A, and A is the ratio of the distance by which the position sensor deflects from the balance position to the maximum stroke of the position sensor; and the drive device is used for receiving the drive command to drive a mandrel of a string ball to rotate according to preset actions so that the string tension can be accurately controlled. By means of the reciprocating type numerical control cored string ball tension control method, the tension can be stabilized within 1-2 seconds, the labor intensity of workers is greatly relieved, and the yarn winding quality can be better ensured.