The invention discloses a quantitative loading system and a semi-automatic loading method thereof, and belong to the technical field of material loading. The quantitative loading system and the semi-automatic loading method thereof solve the technical problems of accurate metering of loading capacity and reduction of workload of personnel. The quantitative loading control system comprises a PLC (programmable logic controller), a display module and an acousto-optic prompt module, IC (integrated circuit) card readers are arranged at initial positions of a plurality of loading areas, an ash siloand a slag silo are arranged above the loading areas at intervals, a cantilever support is arranged between every two adjacent loading areas, a display module and a parking signboard are hung on eachcantilever support, a plurality of sets of laser spotlights are arranged on the side edge of one side of each loading area according to the axle distances of different loading vehicle models, and a laser signal receiving device is arranged at the position, corresponding to the laser spotlight, of one side of the loading area; and each of the ash silo and the slag silo comprises a hopper, a feedingarticulated chute and a discharging articulated chute, and an impeller feeder, a flow sensor and a discharging control valve are mounted on each of the feeding articulated chute and the discharging articulated chute. According to the quantitative loading system and the semi-automatic loading method thereof, the loading efficiency is improved, the manual workload is reduced, and the economic benefit is improved.