PURPOSE: To provide a coupling system capable of feeding a yarn feed package wound back by a pirn winder to a double twister in simple constitution.

CONSTITUTION: Both machines of a double twister 2 having a spindle in which a bobbin is fitted and a pirn winder 1 are coupled with a carrying rail 3 and a carrying unit 12 hanging down plural bobbins on the carrying rail 3 by a holding tool is traveled, and also the carrying unit 12 is freely lifted or lowered by lifting arid lowering rails 71 and 29 of each machine and simultaneously, a pitch P of the holding tool of the carrying unit 12 coincides with a spindle pitch P of both machines 1 and 2.