The invention discloses optical channel protection method, device, apparatus and system, relating to the communication field and solving the problem that the optical channel protection apparatus is complex to upgrade and thus brings relatively high upgrade cost. A sending end and a receiving end are separately provided with a second level module connected with a first level module, wherein the second level module of the sending end determines a first protection channel for outputting a protection signal from at least two first protection channels and outputs the protection signal received from the first protection channel; the second level module of the receiving end determines a third protection channel for receiving the protection signal from at least two third protection channels and outputs the received protection signal through the third protection channel. The invention is applicable to optical channel transmission.