The invention discloses a chain plate line with an on-line derailment detecting device. The chain plate line comprises a chain plate line body and the detecting device. The chain plate line body comprises a chain plate line main body, a driving chain wheel, a driven chain wheel, a motor and a speed reducer. The chain plate line main body is a closed annular line body, and the two sides of the chain plate line main body are provided with chains correspondingly. The driving chain wheel engaged with the corresponding chain is arranged at one turning body of the chain plate line main body, and the driven chain wheel engaged with the corresponding chain is arranged at the other turning body of the chain plate line main body. The detecting device comprises supporting devices, detectors and a detection control box. The supporting devices are arranged on a support and located at the two sides of the driven chain wheel, and the supporting devices are positioned over the chain plate line main body. The supporting devices are sleeved with the two detectors, and the two detectors get close to the inner side of the chain plate line main body. By means of the chain plate line with the on-line derailment detecting device, faults that the chain plate line main body deviates from guide rails and is disengaged can be detected in an on-line mode, the chain plate line can be stopped suddenly, and therefore damage to the chain plate line can be reduced, and the production efficiency and benefits can be guaranteed.