The invention provides an automatic control system for sintered mixture moisture. By measuring the wet capacity of the sintered mixture, predicting proper water content of the sintered mixture according to the wet capacity and adjusting and controlling the water adding amount of a granulating process according to the proper water content prediction value and the on-line detected practical water content to finally stabilize the water content of the sintered mixture at a proper value, the system realizes automatic control of the optimal water distribution quantity of the granulating process and on-line real-time control, effectively overcomes the defect that the water distribution quantity precision manually controlled at present is difficultly ensured, and greatly reduces the labor intensity of operators; and meanwhile, the system has the advantages of short control and stabilizing time and low fluctuation, and effectively overcomes the defect of water distribution quantity error caused by objective factors such as climatic change and the like.