The invention discloses a method for optical cable fault diagnosis. The method comprises an optical time domain reflectometer, optical cables, an intelligent optical cable splice closure; the opticalfiber is connected with the intelligent optical cable splice closure; optical fiber breakpoint binary encodings are located in the intelligent optical cable splice closure, the intelligent optical cable splice closure realizes the intercommunication of the optical cables; the optical time domain reflectometer is connected with the optical cable; if the optical cable is in fault, each optical fiberbreakpoint binary encoding is compared with the saved corresponding binary encoding, the absent binary encoding is acquired through the comparison, and then the breaking location of the optical cableis determined. The problem that the reference point precise technology identification in the optical cable cannot be realized since the optical recognition, the ranging and the accurate geographic information cannot be effectively combined in the prior art is solved.