The utility model discloses a controller of a ring main unit. The controller includes a current sensor, a voltage sensor, an A/D converter, an optoelectronic isolator, a digital signal processor, a power supply, a microprocessor, a GPRS module, a keyboard, a display, a USB interface and a memory. The current sensor and the voltage sensor are respectively connected with the A/D converter; the A/D converter, the optoelectronic isolator, the digital signal processor and the microprocessor are sequentially connected; the microprocessor is respectively connected with the GPRS module, the keyboard, the display, the USB interface and the memory; and the power supply is respectively connected with the digital signal processor and the microprocessor. The controller of the ring main unit is simple in structure and low in cost, can monitor and control the ring main unit, and defect faults of the ring main unit.