Abstract: In this paper, the experiment about the monitoring errors probability and the average performance time of different digital features were studied when the operator performed the procedures in the main control room. The simulation experiments were designed through field investigation to nuclear power plants and interviews with operators. The results show that the monitoring errors probability in color was 1.71×10^-3, and that in figure was 1.57×10^-3, but the physical form of monitoring object had no significant effect on the monitoring errors probability. The more complex the interface management tasks（the more the navigation）, the longer the average performance time. Monitoring errors probability of 3 times of navigation was significantly less than that of 1 or 2 times. The results of monitoring errors probability and average performance time in different numbers of monitoring objects were significantly different. The more the monitoring objects, the higher the monitoring errors probability and the longer the average performance time, that is to say, the reliability of monitoring behavior is lower.