The invention relates to the technical field of beneficiation, in particular to a control system and control method of ore grinding ore granularity. The control system of the ore grinding ore granularity comprises a human-computer interface unit, a detection unit, a central data processing unit and an executing unit. Set parameters related to the ore grinding ore granularity are set in the human-computer interface unit, actual parameters related to the ore grinding ore granularity are detected in real time through the detection unit, and the actual parameters and the set parameters are intelligently analyzed and judged through the central data processing unit. Then, the executing unit is used for controlling related actions, and the proportion of large ore, medium ore and small ore is kept within the range of the set parameters. The stability of the ore amount is guaranteed through automatic control, and the optimal granularity level distribution of feeding ore is guaranteed. The ore grinding efficiency of a semi-automatic ore grinding machine is greatly improved, and the overflow concentration and fineness of a whirlcone are improved to a certain degree.