This paper reports on an experimental study on human-machine interface in LED manufacturing systems to measure the influence of information overload on user experience. The results are based on cognitive ergonomics. The experiment used eye-tracking methods and a questionnaire to gather data. The independent variables were interface complexity and user background. Interface complexity had three levels: high interface complexity, moderate interface complexity and low interface complexity. User background had two levels: the novice group and the expert group. The dependent variables included time to first fixation, fixations before and subjective feelings. A total of 38 operators participated in the experiment, and the results showed that (1) interface complexity caused a significant difference in time to first fixation (P \ 0.05) and fixations before (P \ 0.05). Furthermore, the results revealed significant differences between high complexity interfaces compared to low complexity interfaces (P \ 0.05). However, no significant differences were observed between moderate and low complexity interfaces or between moderate and high complexity interfaces (P [ 0.05); (2) user background significantly affected the user experience; (3) within the same complexity level, expert operators' cognitive workload was significantly lower than that of novice operators; and (4) there was no significant relationship between the interface complexity and the user's background. The study concludes that because interface complexity has a significant effect on the time taken to locate the target button on the screen, interface design should be as simple as possible, while still providing the necessary level of functionality.