Current process of aggregate tank loading in many construction processes in China is still by the traditional simple electrical control with manual work, there are problems such as difficult to control the material flow, low efficiency and poor safety. Based on the structure optimization of the traditional aggregate bulk loader, the design of the precise discharging control system of the aggregate bulk loading machine using rotary valve and Mitsubishi PLC was proposed, and the structural design and the PLC control system development were completed. The control system realizes the continuous and automatic drop of raw materials in the aggregate bulk loader, and can automatically close the valve when the utility power is off. It has been verified by the actual production that the aggregate bulking machine works well, which promotes the production efficiency and improves the quality efficiency of the construction site filling construction.