Abstract: The instrumentation and control system is digitized in nuclear power plants, which makes the operator’s situation awareness error (SAE) more prominent. In order to identify the existing main SAE and carry out prevention and control, the SAE was classified first from the perspective of cognitive function in situational awareness. And then, the collected human factor events were analyzed by using the established SAE analysis method, in which data of 79 samples were obtained to identify the main SAE and causes. Based on the perspective of defense in depth, the systematic prevention, control and recovery system of SAE was proposed from three aspects, including prevention in advance, control during implementation and post-recovery of SAE. The results of the present work may provide theoretical guidance for prevention and control of SAE in digital nuclear power plants.