The invention provides a simple, stable and accurate balance control system for the grinding quantity of a horomill, comprising a feed metering device, a feed back metering device, a material balance controller, an upper PC(personal computer) system, a cable and shield control signal wires, wherein one end of the feed metering device is positioned below a feeding port of the system, and the other end of the feed metering device is connected with a feed inlet of the horomill; one end of the feed back metering device is positioned below the outlet of a separating device, and the other end of the feed back metering device is connected with the feed inlet of the horomill; the feed metering device and the feed back metering device are respectively connected with the material balance controller through the shield control signal wires; and the material balance controller is connected with the upper PC system through the cable. During operation, the feed metering device and the feed back metering device reflects the feed quantity and the feed back quantity respectively through the shield control signal wires to the material balance controller, and then the operating personnel can adjust the flow rate of material according to the display condition of the upper PC system, thereby fully controlling the balance of on-line material.