To provide the subject system so designed that the operation mode of carriages for piecing operating is rendered variable via a central control unit to reduce the frequency of unnecessary piecing operations so as to utilize the carriages.

This system is so designed that the operation mode of at least carriages T for piecing operation is rendered variable via a central control unit. It is preferable that the change in the operation mode is at least that in the frequency of piecing operation trials or the travel speed of the trucks T, and besides, the production efficiency of a spinning machine S is calculated using, as variable, piecing work trial frequency, the number of spinning units (s) under the charge by a single operator or the travel speed of the trucks T, and based on the result, the operation mode of the carriages T is set.