The invention relates to a system and a method for producing calcium carbide by utilizing carbide slag. The system includes a purification unit, a drying and conveying unit, a centrifugation unit, a calcining unit and a calcium carbide unit, wherein the above units are arranged in sequence. The purification unit comprises a carbonization unit and a press filtration unit. The carbonized solid slurry inlet of the press filtration unit is connected with the carbonized solid slurry outlet of the carbonization unit. The carbonized solid outlet of the press filtration unit is connected with the inlet of the drying and conveying unit. The centrifugal carbonized solid inlet of the centrifugation unit is connected with the outlet of the drying and conveying unit. The calcining carbonization solid inlet of the calcining unit is connected with a centrifugation and carbonization solid outlet. The calcium oxide powder inlet of the calcium carbide unit is connected with the calcium oxide powder outlet of the calcining unit. According to the technical scheme of the method for producing calcium carbide, the CO2-containing gas is introduced into the carbide slag slurry, so that the carbide slag slurry is purified. In this way, the problem that the carbide slag is difficult in treatment can be solved. Meanwhile, the low-cost and low-pollution production pathway of the calcium carbide is fundamentally realized.