To achieve effective control and monitoring of flexible HVDC converter based on MMC topology at a high voltage large capacity, this paper designs a flexible HVDC valve control system based on VME master-slave bus architecture. The system selects the MVME6100 as main VME processor, and uses boards based on the SPARTAN-6 and VIRTEX series high performance FPGA as VME slave processing unit. The slave processing boards accomplish VME slave communication protocol, Aurora protocol and IEC60044-8 protocol as underlying communication mechanisms. This system adopts the VxWorks hard real-time operating system development application, and implements the Nearest Level Modulation algorithm and circulating current suppressing functionality, which can realize control period up to a hundred micro-seconds and can meet the real-time control and monitoring requirement of modules up to thousands in the converter. After RT-LAB simulation test, the system meets the requirements of data transfer rate of 200 levels system and the system control specification.