The present invention provides a vanadium redox flow battery control system based on PLC. The control system comprises a vanadium redox flow battery process system and a control cabinet. The control cabinet comprises an alternating current power supply configuration unit, a direct current power supply configuration unit, an ion concentration measurement unit, a man-machine interface unit, a control unit, a signal transmission module group and a power frequency conversion unit. According to the present invention, a power supply circuit of the control system, a PLC module group, a I/O module group, the signal transmission module group and the power frequency conversion unit are grouped and independently designed so as to realize the hot redundancy of the whole system, and greatly improve the stability and the reliability of the system. The system has a plurality of operating modes and an external four-circuit alternating current power supply, such that the charging and the discharging of the vanadium redox flow battery can be performed at any time and any place, the operation is convenient and the application is flexible; the system further has functions of self-diagnostic and self-recovery, such that the misjudgment and the missed judgment of the failure are effectively avoided, the reliability and the availability of the system are improved so as to indeed realize unattended operation; in addition, with the man-machine interface, the related parameters can be monitored and adjusted so as to meet the requirements of various operating conditions.