AbstractThe old discharge control system (DCS) with HIDIC-80E mini-computer has been replaced by a control system with a unix workstation and a VME-bus system. Functionally, the workstation performs message communication with VME controller on the network, data processing using plant data and data acquisition. The commands and receiving the status data in real time. The new DCS is flexible for system extension and able to quickly respond to various requirements of software modifications. The data acquisition speed has been improved by almost a factor of two over the old one. Troubles and countermeasures experienced in the replacement work are also presented.