The invention belongs to the technical field of hot rolled section steel equipment, and relates to a roller way device with a roller body capable of being disassembled on line and a disassembling and assembling method. The roller way device comprises a roller shaft part and a roller body part which are connected through a fastener. The roller shaft part comprises a roller shaft and conical clamping groove parts; the roller body part comprises a roller body, a conical shaft and connecting plates, the roller body is composed of two half roller bodies, and the two half roller bodies are of a 180-degree semi-circular ring structure. The four conical clamping groove parts are welded to the roller shaft and arranged in a 90-degree symmetric mode, the half roller bodies and the conical shaft are welded together through the connecting plates, two connecting plates and the conical shaft are welded to each half roller body, and a 90-degree included angle is formed between every two connecting plates and the conical shaft. The welded half roller bodies, the connecting plates and the conical shaft are installed in the conical clamping groove parts of the roller shaft and fastened through fasteners. The worn roller body can be fast replaced on line, labor intensity of workers can be greatly relieved, and the cost of spare parts is reduced. The roller way device has the advantages of being simple in structure, fast to operate and low in manufacturing cost.