In order to explore the mental workload levels of pilots at different stages of airfield traffic pattern, search for electrocardiogram indicators that represent mental workload, a six degree of freedom simulation flight experiment on pentagonal flight tasks for pilots was conducted, the mental workload levels during the flight process was measured, data on various electrocardiogram (ECG) indicators of pilots at different flight stages was collected, and factor analysis was used to construct a pilot mental load model to analyze and verify the characteristics of changes in the mental workload of pilots at different flight stages. The results indicate that compared to heart rate indicators, heart rate variability indicators have higher reliability and validity in measuring pilot mental workload. The mental workload during takeoff and ascent stages is at a relatively low level and shows a decreasing trend. The cognitive load level during the cruise phase is low and the trend of change is smooth. The mental workload level during the approach and landing phase is the highest. In addition, unexpected events can significantly affect the mental workload, causing a significant increase in the pilot's mental load.