Abstract: In order to ensure safety of railway transportation, with train operators as research objects, relationship among their work stress, salivary cortisol (also known as stress hormone), stability of work performance, and positive and negative emotions was analyzed. Firstly, through literature review, a hypothesis was put forward that cortisol could feel changes of emotions and cognitive ability, both of which had potential of influencing operators' stability of work performance. Then, valid questionnaires of 68 objects, their samples of' saliva cortisol and work performance over the next 6 months were collected. The results show that the more stress they feel, the higher level of saliva cortisol they will have together with worse cognitive ability and more negative emotions, and moreover, their performance for the following 6 months will be more unstable. Saliva cortisol is highly correlated with operators' safety behaviors, and improving their pressure resistance ability will lay a solid foundation for safe production of enterprises.

Key words: cortisol, railway transportation, operators, negative emotions, safe production