The invention relates to the technical field of waste paint slag treatment, and discloses a waste paint slag harmless treatment system. The waste paint slag harmless treatment system comprises a material treatment system and a gas circulation treatment system matched with the material treatment system. The material treatment system comprises a material receiving area, a treatment area, a filling sealing area and an outer packaging area, all of which are connected through a connecting device. The gas circulation treatment system comprises a gas conveying device and a tail gas absorbing device penetrating the whole material treatment system. According to the provided waste paint slag harmless treatment system, on one hand, energy consumption is reduced to the maximum degree through layout optimization, on the other hand, a waste paint slag barrel which must be manually operated originally is opened, material transmission among the waste paint slag pouring procedure and various procedures is optimized into mechanical transmission, the work efficiency is greatly improved, and the work intensity of operators is reduced; and meanwhile, the exposure time of the operators in harmful gas is greatly shortened, the health risk of the operators is reduced to the maximum degree, and wide application prospects are achieved.