A Control system for the XFEL/SPring-8 magnet power supply was designed by using an FPGA program in the "i-DIO" card. This card is modified of the VME field bus card "Opt-VME DIO". An output current deviation, monitoring ADC data from DAC current set value, is checked and makes an alarm signal. The ADC data can be averaged in some special sequences commanded by an upper workstation. A local control system of the power supply is also achieved by the i-DIO. Magnet power supply total system and test operations with the newly developed i-DIO card will be reported.