The invention relates to a method for realizing ODUK (Optical Channel Data Unit) protection switching by a crossed disc of OTN (Optical Transport Network) equipment. The crossed disc of a network element A is located at a switching state under the protection of an ODUK; if an alarm in a reserved direction is further detected, whether the alarm is caused by a self-loop test is judged; and if the alrm is caused by the self-loop test, reserved alarm information happening at the moment is judged to be caused by the test and a switching state is maintained. An immediate response method is adopted to process the reserved alarm information under a normal work condition and outside delayed time, so as to recover master processing. The method for realizing the ODUK protection switching by the crossed disc of the OTN equipment is convenient for an engineering field OTU (optical transform unit) business test. A protection method of source double ends connected with an instrument, which need to be detected and are protected in the prior art is changed to the method of realizing the protection switching, which supports that one end is connected with the instrument and other end is looped to test, so as to save manpower and material resources.