Abstract: A method and a system of production control for a production line composed of a plurality of automatic machines, in which input of control data and change of contents of the data required for control of the automatic machine can easily and efficiently be made. Identification data fed from the host computer (30) are converted by a data converter (31) into control data for automatic machines (11) in each process and stored in a storage medium (20) so that each automatic machine may be controlled after the storage medium has been moved together with the workpiece, by control data read out from the storage medium in each process in the production line. The storage medium store not only control data for the workpiece moving together with this storage medium but also those for a plurality of work pieces positioned on the upstream side of the workpiece in the production line and, thereby, prepares the relative automatic machines to be ready for the subsequent stage of operation.