The work aims to investigate the effect of character size and colour consistency on the visual search efficiency of information in the ECG monitor interface in the presence of fog on the goggles. By simulating the scenario of the goggles under different fog levels and controlling different character sizes and color consistency, the effect of the three factors on the visual search efficiency of the health care workers was examined. In the experiment, 37 subjects completed the eye movement experiment successively, and their behavior and eye-movement data were recorded to explore the interaction effect of the three variables in depth. The results of the study found a significant interaction effect among the three factors of different fog levels, character size and colour consistency when the ECG monitor was used, with a significant P < 0.001 interaction of the three factors for the behavior data and a significant P < 0.05 interaction of the three factors for the eye movement data. Under no fog and low fog, the visual search efficiency of large character and color inconsistency was the highest. Under medium fog and high fog, the visual search efficiency of medium character and color inconsistency was the highest. The visual search efficiency of the interaction effect differs under different conditions of the three factors. Designers can adjust the character size and color consistency of the ECG monitor interface according to the level of fog generated on the goggles to improve the visual search efficiency of the health care workers.